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Transcript 
ant
FINAL THESIS
The Impact of OSPF Routing on Military MANETs
By Rocco Mark Lupoi
Supervised By Dr Grant Wigley
Abstract
This paper establishes the costs and impact that OSPF Routing has on Military style MANETs for use
in the field. The research includes the simulation, recording and analysis of military MANETs to
determine the impact an ‘off the shelf’ routing algorithm such as OSPF has on such a mobile ad hoc
network similar to that in use in the field.
Page i
Declaration
I declare that this thesis does not contain, without prior acknowledgement or permission, any
material(s) submitted for a degree of diploma within the University. To the best of my knowledge, all
material previously published or written by the author has been cited by the correct author(s).
Rocco Mark Lupoi
December 2015
Page ii
Acknowledgements
I would like to thank Dr Grant Wigley and the DST Group for giving me the opportunity to undertake
this research and giving me the motivation to continue my research through the application of a PhD
at the University of South Australia. I would also like to thank the University for giving me the
opportunity to research and undertake this minor thesis through my bachelor of Computer Science.
In particular from the University I would like to thank Dr Grant Wigley and Dr Stewart Von Itzstein. I
would also like to thank Mr Tom Schar and Mr Peter Boyd for providing the support and the
opportunity from the Australia Defence Science and Technology Group for this particular research.
Page iii
Table of Contents
Chapter 1 – Introduction......................................................................................................................... 1
1.1
Statement of Research .............................................................................................................. 1
1.2
Field of Thesis ............................................................................................................................ 3
1.3
Significance and Contributions .................................................................................................. 3
1.4
Outline of Thesis ........................................................................................................................ 4
Chapter 2 – Literature Review ................................................................................................................ 5
2.1 Concept of Military Structure ....................................................................................................... 5
2.1.1 Military Structure ................................................................................................................... 5
2.2 Network Fundamentals................................................................................................................. 8
2.2.1 What is a Protocol? ................................................................................................................ 8
2.2.2 7 Layer OSI Model .................................................................................................................. 9
2.2.3 Layer 2 – Data Link Layer ....................................................................................................... 9
2.2.4 Layer 3 – Network Layer ........................................................................................................ 9
2.3 Concept of Ad Hoc Networks and Mobile Ad Hoc Networks...................................................... 11
2.3.1 Structured Networks ............................................................................................................ 11
2.3.2 Limitations of Structured Networks ..................................................................................... 11
2.3.3 What is Ad Hoc Networking? ............................................................................................... 12
2.3.4 Mobile Ad Hoc Networks and Routing................................................................................. 14
2.4 Network Routing and Routing Protocols/Algorithms ................................................................. 19
2.4.1 What is a Router?................................................................................................................. 19
2.4.2 What is OSPF? ...................................................................................................................... 20
2.4.3 MANET Routing Protocols .................................................................................................... 22
2.4.4 Routing Overheads............................................................................................................... 26
2.4.4.1 Routing Overheads – Metrics ........................................................................................... 26
2.4.4.2 Routing Overheads – Influences ....................................................................................... 27
2.4.5 OSPF on Ad Hoc Networks/MANETs .................................................................................... 28
2.5 Battlefield Variables and Limitations of Communications.......................................................... 31
2.5.1 Limited Bandwidth and Latency........................................................................................... 31
2.5.2 Intermittent Communication Links ...................................................................................... 31
2.5.3 Hidden Nodes....................................................................................................................... 31
2.6 Network Simulation Tools ........................................................................................................... 33
2.6.1 What is a Network Simulation Tool? ................................................................................... 33
2.6.2 Network Simulator 2 and 3 .................................................................................................. 35
2.6.3 OPNET Simulator .................................................................................................................. 35
Page iv
2.7 Conclusion ................................................................................................................................... 37
Chapter 3 – Methodology ..................................................................................................................... 39
3.1 Commonly used Methodologies in Research ............................................................................. 40
3.2 Research Strategy - System......................................................................................................... 43
3.3 Research Validation - Evaluation ................................................................................................ 45
3.4 Research Method to Use ............................................................................................................ 47
3.4.1 Network Behaviour .............................................................................................................. 47
3.4.2 Full System Implementation ................................................................................................ 47
3.4.3 Full System Simulation ......................................................................................................... 48
3.5 Network Simulation Tools ........................................................................................................... 50
3.6 Summary ..................................................................................................................................... 51
Chapter 4 – Simulation Design .............................................................................................................. 52
4.1 Military Structure ........................................................................................................................ 53
4.1.1 Military Symbols................................................................................................................... 54
4.2 Network Topologies .................................................................................................................... 59
4.2.1 Structured Topologies .......................................................................................................... 59
4.2.2 Dynamic Topologies and the Limitations of Structure......................................................... 61
4.2.3 OSPF and Network Structure ............................................................................................... 61
4.3 Representation of Military Structure as a Network Topology/Scenarios ................................... 64
4.3.1 Requirements Provided ....................................................................................................... 64
4.3.2 Defining Military Organization ............................................................................................. 64
4.3.3 Converting to Network Topologies ...................................................................................... 71
4.3.4 Developing Network Cases .................................................................................................. 75
4.4 Determine Inputs for the System................................................................................................ 76
4.5 Determine Outputs (metrics) for the System ............................................................................. 77
4.5.1 IP Forwarding Tables ............................................................................................................ 77
4.5.2 OSPF Traffic .......................................................................................................................... 77
4.5.3 Point to Point Throughput ................................................................................................... 78
4.6 Summary ..................................................................................................................................... 79
Chapter 5 – Simulations ........................................................................................................................ 80
5.1 Simulation Phases ....................................................................................................................... 81
5.1.1 Phase 2 ................................................................................................................................. 82
5.1.2 Phase 3 ................................................................................................................................. 89
5.2 Simulation Results ....................................................................................................................... 95
5.2.1 Phase 2 ................................................................................................................................. 95
5.2.2 Phase 3 ............................................................................................................................... 117
Page v
5.3 Summary of Simulation Results ................................................................................................ 138
Chapter 6 – Conclusions and Future Work ......................................................................................... 140
6.1 Future Work .............................................................................................................................. 142
6.2 Thesis Contribution ................................................................................................................... 143
References .......................................................................................................................................... 145
Page vi
Chapter 1 – Introduction
The following section will give a synopsis of the purpose of the research on MANETS, what aspects
this paper will address, and what will be contributed within the research.
1.1 Statement of Research
The research proposed in this paper will focus on Mobile Ad Hoc Networks (MANETs) and the
routing overheads of the Open Shortest Path (OSPF) routing algorithm for military use MANETs.
MANETs are an infrastructure-less based networking model that is created purely with end user
devices, rather than using any form of fixed infrastructure or networking devices. Essentially, a
MANET puts the work of creating and maintaining a network in the hand of end devices rather than
dedicated networking equipment such as routers and/or switches. Routing overheads refer to the
amount of networking resources that are required to upkeep the routing of data throughout a
network. Routing overheads are one of the most prevalent concerns when it comes to MANETs, as
limited resources, low bandwidth devices, power limitations, energy limitations and the dynamic
nature of MANETs will further increase the overhead of routing on such a network, resulting in a
further consumption of networking resources by the routing protocol. These limitations are even
more prevalent on military MANETs, where harsher environmental variables, larger network/node
sizes, and a limitation on device infrastructure create a further drawback for routing overheads.
The applications for MANETs are most optimal when creating infrastructure for a network is either
impossible due to environmental or cost limitations. MANETs also have the advantage of removing a
single point of failure of the network, as they are non-administered. This means that the network is
self-configuring and self-maintained, and thus will not break down as a network that is administered
by a particular device would. This thesis is intended towards the research of military MANETs for the
DST Group (Defence, Science and Technology Group).
The utilization of routing protocols on a MANET poses one of the most prevalent issues when trying
to establish a MANET. As stated earlier, routing overheads are the major concern with routing within
a MANET environment. The core influence for routing overheads is the routing protocol itself. This is
due to the protocols themselves holding the policies and algorithms used to determine the route
each data packet should travel on the network. Routing algorithms that are designed for use on
conventional structured networks are not usually considered in a MANET environment, let alone a
military MANET environment with further limitations. This is due to factors of the way the routing
protocols themselves function internally. These conventional routing protocols were not designed
for use on MANETs. That being said, there are plenty of advantages for utilizing such a routing
protocol on a MANET, key of which is the non-specialized and well known nature of said routing
protocols.
The research will focus on one conventional routing algorithm in particular as requested by the DST
Group for evaluation on MANETs. The routing protocol in question is Open Shortest Path First
(OSPF). The research will undertake evaluation of the OSPF routing protocol, which will be
performed through a series of simulations to reveal routing overheads of the routing protocol setup
in a MANET environment.
Page 2
1.2 Field of Thesis
Ad Hoc Networking, Networking, Routing Protocols, Military Networks, Mobile Ad Hoc Networks,
Network Simulation Tools.
1.3 Significance and Contributions
The following section will outline the contributions, which will be made in this thesis.
-
OSPF in a military MANET situation is unlikely to be viable with the mobility model. (Chapter
5)
-
With a low number of nodes (less than 5 soldiers), the use of RIP and/or OSPF might be a
viable routing solution on a military MANET. (Chapter 5)
-
OPNET Network Simulation model for military MANETs. (Chapter 4)
-
Expansion of the understanding of use of MANETS within the hierarchical structure of the
Military and the use of the MANETS within this structure. (Chapter 4)
-
Expand the understanding of the limitations of the OSPF routing algorithm. (Chapter 6)
Page 3
1.4 Outline of Thesis
The following section will provide an outline of each of the chapters presented in the thesis.
Chapter 1 - The thesis will be introduced, giving a brief overview of the expectations of the
following research, as well as the Field of Thesis and the Significance and Contributions. The
context for the research will be established and its purpose discussed.
Chapter 2 - This chapter will commence the literature review. This section introduces the
theoretical framework adopted for this study and reviews the literature associated with the
research.
Chapter 3 - This chapter will cover the gaps found in the literature in Chapter 2, and develop a
research question for the thesis. The methodological approach to the research question will
then be developed and explained.
Chapter 4 - This chapter will cover first phase of the methodology as explained in the Chapter 3.
This is the first stage in developing a system to help answer the research question. This
section begins by detailing the theory required prior to designing the system to answer the
research question.
Chapter 5 - This chapter includes the development of the system and the gathering/evaluating
of results. This section focuses on the results and analysis of the study.
Chapter 6 - This chapter will conclude the research by giving a final word on the results as
gathered and analysed in Chapter 5. This section will also go into detail of any future works
that have been developed from the conclusion of the research.
Page 4
Chapter 2 – Literature Review
The following section will commence the literature review of the research. This section will go into
building up information on military structure, networking, ad hoc networking, mobile ad hoc
networking, routing overheads, as well as networking simulation tools. All information presented in
this section is based upon research found in research papers, journals, conference papers, lectures
and presentations.
2.1 Concept of Military Structure
Like any team based organisation or group, the military adheres to a structure that helps define
rankings of power, positioning of people, as well as task separation and allocation of those people.
There are many proven key advantages to the utilization of team-based structures in solving
problems. [1] Some of these include the ability to capitalize on team member’s strengths and
minimize their weaknesses. A team structure allows the coverage for all activities depending on the
member’s abilities. [2] When this structure is adhered to, it creates a strong force that can capitalize
on members to ensure there are less management, improved relationships, increased productivity
and a good balance to both the people and the task at hand. [1]
The following section will briefly explain why the military have such a structured team system. From
this, research will also be undertaken into the variables and limitations one can combat in a
battlefield regarding environmental and technological constraints.
2.1.1 Military Structure
The most basic and important resource of the Army is its soldiers. In carrying out the mission of
defending a nation, people in the Army, both soldiers and officers must work closely as a team to
execute complex tasks under difficult and dangerous conditions. There are three critical components
to the succession of military organization. These include: [2]

A system of rank reflecting a person’s responsibilities and experience.
Page 5

An organizational structure in which people know their responsibilities.

Military courtesies, customs, and traditions that serve to bond military professionals
together.
It is important to note that there are two major components that we will be focusing in the scope of
this research. They include Army Rank and Army Unit Structure. Both of these components are vital
to the understanding of the military organization and reveal how the main focus of this research will
be approached. It is important to understand these key pieces of information, as this is the defining
structure upon a system needs to be built.
2.1.1.1 Army Rank
Army rank and military rank is what binds all military personnel together as a team. In the army, this
relationship is known as the ‘chain of command’. Army rank identifies who is in charge. This defines
whom to look for orders, guidance, and leadership. This ranking works on the hierarchical chain of
command, with the most important leadership roles sitting at the top of this chain. At this stage it is
important to note that the ranking is hierarchical works via a chain of command. More detail on the
ranking and the workings internal to the military we will be focusing on will be fleshed out further
into the research. [2]
2.1.1.2 Army Unit Structure
In an Army Unit structure (also referred to as a ‘Cadet’ command structure), the work of the overall
team is carried out in both smaller and larger organisations. The most significant of these are the
squad, platoon, company and battalion. These smaller organisations are ranked in the same respect
as the Army Rank previously described. The types of people that work in these smaller organisations
are grouped according to rank and their job. [2] For example, there may be a dedicated quad of
snipers.
It is also important at this point to note that these smaller organisations are also ranked in a
hierarchical order or chain of command in the same way that soldiers and officers are ranked. In this
Page 6
respect we have a group of people working in groups at levels up the chain of command in a
structured and hierarchical manner towards the top of the chain; similarly to how most enterprises
and organisations function. More detail on the army unit structure and the internals to each of the
organizations and where they sit on the hierarchical chain of command will be further fleshed out
further into the research.
Page 7
2.2 Network Fundamentals
This section will introduce the basics of networking and routing. The main focuses of this section
include the 7-layer OSI model, routing and common routing protocols/the basic operation and
workings of a routing protocol. A network can be defined as a group of devices that are connected
together to share and transfer data along either a physical medium, or wireless connections. When
networks become increasingly complex with the utilization of more devices and other more complex
requirements, it is essential to have other devices on that network to maintain the connections
between the devices that require communication on the network. These devices are known as
‘network devices’ and can include routers, switches, wireless gateways, network interface cards and
wireless cards. Devices that are typically used within a network include client computers, servers,
phones, tablets, and other networking equipment.
2.2.1 What is a Protocol?
A protocol (in networking terms) is a set of rules that governs the communications between
computers (and/or devices) on a network. In order for two devices to communicate with each other,
they must be speaking the same ‘language’. Many different types of network protocols and
standards are required to ensure that the device (no matter what operating system, networking
interface card, or application being used) can communicate with other devices on the same network.
[7] Protocols are generally expressed through packets. Packets are essentially protocols that can
handle data. An example of this is the Transmission Control Protocol (TCP) that sits at Layer 4 of the
OSI model (the Transport Layer). The TCP is used for sending reliable data over the Internet. This is
achieved by using a checksum to ensure the data is contained within the packet, to ensure that the
data is accurate and reliable. The User Datagram Protocol (UDP) on the other hand, is used in a
similar manner to the TCP, but due to its lesser complexity, it is more speedy and efficient, but has
its fall-backs in reliability and accuracy. Protocols are usually used within packets, which are a unit of
containing overheads/relevant packet information and encapsulated data.
Page 8
2.2.2 7 Layer OSI Model
A reference model is a conceptual blueprint of how communication should take place. It addresses
all of the processes required for effective communication and divides these processes into logical
grouping called layers. A communication system that is designed in this way is known as a layered
architecture. In networking, the basics of protocols, packets and lower level communication can be
expressed through the developed Open System Connection (OSI) model. [6] The OSI model is
comprised of seven different layers, each layer having its own responsibility. The OSI model includes
the Application, Presentation, Session, Transport, Network, Data Link and Physical layers. Each of
these layers is grouped by a protocol data unit (PDU). The PDU represents what network protocols
each layer focuses on (this will be covered in Section 2.2.2). The protocols include Data (Found at the
Application, Presentation and Session layers), Segments (Transport), Datagram (Network), Frame
(Data Link) and Bit (Physical). For the sake of relevance of this research we will only be focusing on
Level 3 and Level 2 of the OSI Model (respectively Network [L2] and Data Link [L3]).
2.2.3 Layer 2 – Data Link Layer
The Data Link Layer functions in a similar way to the Network Layer (section 2.2.4). The key
difference is it responsible with Media Access Control (MAC) between nodes. MAC includes error
corrections and acknowledgements within the physical layer as well as delivery of frames within a
local network. The Data Link Layer is typically sub layered between the Logical Link Control (LLC)
layer and the Media Access Control (MAC) layer. [6]
2.2.4 Layer 3 – Network Layer
The network layer is used for mainly routing, normally using routers. The layer is critical towards
end-to-end connectivity of devices. This is due to the fact that this layer maintains source and
destination between hosts within a network. It also maintains segmentation of networks and sub
networks. [6]
Page 9
As routing occurs at this layer (Network Layer), this research will focus on the protocols that operate
within the Network Layer. Standardized Network Layer protocols are typically used in structured,
enterprise networks and is uncommon with military use, especially within mobile ad-hoc networks
(MANETS). However, for the purpose of this research, it is important to acknowledge such protocols
and reason with their suitability/unsuitability within MANETS. This will be further fleshed out later
on in the research.
Page 10
2.3 Concept of Ad Hoc Networks and Mobile Ad Hoc Networks
The previous sections have outlined the basics of military structure, the purpose of such structure, as
well as the basics of networking and the purposes of the network layer protocol. This section will
further expand on ad-hoc network infrastructure, and why a structured network may not be suitable
within a military.
2.3.1 Structured Networks
A structured networking infrastructure is a fixed, predictable network topology, which uses
specialised devices (such as routers) to maintain communications. Each of the networks that have
been explained within the previous sections are examples of structured networks. There is a key
difference that separates structured networks from unstructured networks. That key difference is in
the respect that structured network topologies change a lot less frequently in comparison to
unstructured networks. Network topologies usually change for a structured network due to
environmental issues outside of the control of network administrators (ie. An electrical storm
causing a power outage), a change of configuration due to a restructure, or possibly the addition of
new hardware. The change of network topologies can be very costly, as information of the topology
change must be between routing nodes within the network.
Structured networks are also very organised (as one would assume with the name). Typically within
a structured network, special devices are required to perform specialised tasks. Typical structured
enterprise networks utilise the core, distribution and access layer. The core layer utilizes Layer 3
Networking/Routing and acts as the backbone for the while network. The distribution layer utilizes
both Layer 3 Networking and Layer 2 Switching, depending on the size of the distribution layer. The
access layer is purely for switching and brings connectivity for end devices.
2.3.2 Limitations of Structured Networks
There are many advantages to the utilization of structured networks. There is a reason that most
enterprise and standard networks are based around the ideas and concepts of structured network
Page 11
topologies. They are very reliable for their intended purpose (usually within an
office/home/enterprise application). This section will go into explaining some of the key limitations
when it comes to structured networks, with the later sections also going into further detail as to why
structured network topologies may not be the best solution in the context of military ad hoc
networks.
One of the key disadvantages of the use of structured networks comes in the lack of flexibility for
nodes to connect to any part of the network. This comes as a major disadvantage to the flexibility
that MANETs offer in comparison to the structured nature of enterprise networks. As previously
described, the typical core, distribution, access layer only allows access to a network through an
access layer. In some situations it is required to have access throughout the whole network. As
shown in [8], the article describes a MANET that allows the flexibility of devices to connect
simultaneously on the network, with dropouts handled by the flexibility of the reconfiguration of the
network on-the-fly.
Another major disadvantage of structured networks is that they have a central network
administration to oversee and maintain the network as required. This is configured by network
administrators, which required a constant maintenance and repair to ensure the network is up kept
and reliable.
Lastly, structured network topologies have typically very high/expensive routing costs. This is usually
due to the sheer amount of devices on such networks, but also has a factor with the actual routing
technologies that are utilized at the Network Layer for routing purposes. The more devices on the
network will typically require more specialised network devices and more layered/structured routing
configurations.
2.3.3 What is Ad Hoc Networking?
Simply put, an ad hoc network is a network formed without any central administration, which
consists of mobile nodes that use a wireless interface to send packet data. Since the nodes in a
Page 12
network of this kind can serve as routers and hosts, they can forward packets on behalf of other
nodes and run user applications. [9] Ad hoc networking provides a natural self-healing, selfconfigurable network ecosystem, which requires little maintenance. This is due to ad hoc networking
protocols being structured around each node being its own router and is ware of every other node
on the network. This key concept of each device essentially being a ‘router’ allows the connectivity
of nodes at any point throughout the network, giving the flexibility of mobility.
2.3.3.1 Problems with Ad Hoc Networking
While the concepts and the advantages of ad hoc networking seem almost too good to be true,
there are always some key disadvantages that need to be explained before carrying on with the
research.
Due to the rapid nature of ad hoc networks in comparison to structured networks, it is very difficult
to find/use a networking routing protocol. All of the current known and developed network routing
protocols have been developed for the use in structured networks. For that reason it must be taken
into consideration that it will be difficult to adapt said protocols for the use in MANETs. For example,
one of the most common routing protocols which is the focus of this research (Open Shortest Path
First [OSPF]) relies upon flooding packets within the network to maintain a consistent topology for
all routers within the network. While this flooding is normally seen as a very low cost and fast
update in wired networks, it is a different story without the reliability of wired links. Error rates on
wireless links are increased, speed and throughput is decreased and bottlenecks are introduced with
the device capabilities transmitting said wireless signals. As OSPF is very rapid with its updates, there
may be nodes dropping/needing to be re-added to the topology due to a packet flood not making its
way to some nodes. OSPF also relies of neighbour adjacencies (nearby nodes), which within an ad
hoc network can be forever changing as mobile nodes move around a lot. There will be more
information on OSPF on MANETs in Section 2.4.4.
Page 13
2.3.4 Mobile Ad Hoc Networks and Routing
Thus far, the concepts of ad hoc networking have been introduced as well as key disadvantages with
both structured networks and ad hoc networks. This section will delve further into the
implementation of ad-hoc networking in the mobile realm known as mobile ad hoc networking
(MANET). A MANET is a type of ad hoc infrastructure that solely uses mobile devices to structure the
network.
2.3.4.1 Common Applications and Uses of MANETS
It is important to note that MANETs are not normally used in situations where infrastructure,
structured networks are cheaper and easier to set up. It makes little to no sense to set up an ad hoc
network in an office/enterprise environment where by the infrastructure is easily cabled/wired to
suit those needs. MANETs are used where infrastructure cannot be utilised due to the
environmental constraints associated with the location or application of the network. [10] A key
example of this is on the field in a military situation as the focus of this research. Besides the scope
of this research, there are many other examples of a MANET in the field. Another example comes in
the form emergency/rescue operations for disaster relief efforts (i.e. fire, flood, earth-quakes, etc).
In this situation, emergency rescue operations must take place where non-existent or damaged
communications infrastructures are and rapid deployment of a network is needed.
MANETs are also beneficial in infrastructure-less scenarios, which may contain simple tasks and not
require the overheads of a structured network. A good example of this includes the ability to quickly
and easily set up a network for short-range intercommunication between various mobile devices
(such as a PDA, a laptop, and a cellular phone). Tedious and un-necessary wired cables are replaced
with wireless connections.
2.3.4.2 Military use of MANETS
One of the major uses of MANETs is in the military application. The properties of MANETs that most
suit the military come in the self-configuring properties and mobility of such a network design. The
Page 14
environments upon which the military are normally situated in battlefield also have very bumpy
terrain and environmental conditions which further prevent the use of static or structured networks
with any formal infrastructure backings as the case would be in an office environment. Thus, the
MANET takes the advantage here in the case of unforseen breakages and link redirection, the ease
of setting up a network on the fly, as well as the scalability and flexibility of the network topology.
[11] An example of this flexibility can be seen in the diagram below, where by the direct route
(shown in red) of the moving traffic can take other routes to reach either node, even if the middle
node where to loose connection.
Figure 1 - Example of 'self-healing' of MANET [12]
One of the military applications of MANETs includes the ‘pocket radio network’. This network has
been designed to conduct a feasibility report on the usage of packet switched radio communications
to provide reliable computer communications. The DARPA PACKET RADIO NETWORK, PRNET has
evolved throughout the years (1973-1987) and has become a robust, reliable and operational
Page 15
experimental network. The follow up to this program and evaluation is further benefitting from this
research in making lower power, cheaper and smaller radio devices that provide an even better and
more reliable performance in infrastructure-less environments. [13]
2.3.4.3 Advantages of MANETS
There are a multitude of advantages that MANETs provide in comparison to infrastructure-based
networks. One of the key advantages is that MANETs do not require any specific networking devices
such as routers and/or switches to maintain a network. There is no need for a central medium to
ensure that there is full connectivity, therefore allowing a very cheap initial set up cost for the
network. [14]
Another key advantage of MANETS is the ‘self-healing’ ability as described previously. The ability for
routes to essentially never loose connection so long as there is at least one node connection to each
other node allows a full mesh of devices. This full mesh acts as a complete routing map, as each of
the devices act as their own router. When one node looses connection (drops off the network
routing table), it’s link can be ‘healed’ by means of utilizing another connection to reach the
destination node. This ability is done automatically and upkeeps the integrity and reliability of the
network, even when nodes are lost.
The initial setup costs of MANETs are also typically much lower than the counterpart of structured
networks. This is mainly due to the lack of physical infrastructure of the network (i.e. cabling), as well
as the lack of requirement for communication devices such as routers and switches. This lack of
additional equipment leads directly into the next advantage that MANETs provide and that is very
quick setup times and flexibility of the network setup.
The speed upon which a MANET can be setup is also much lower than that of a structured network.
This is due to the almost ‘automatic’ configuration of the network. There is a great separation from
central network administration when using MANETs. This, paired with the ad hoc configuration of
such a network, allows the network to be configured, filled up with devices and operational almost
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instantly once the first node is operational. This flexibility of nodes connecting and moving around
the network also dramatically benefits the use of MANETs in very mobile situations where-by devise
may not necessarily stay in one defined location (both physically and topology defined).
2.3.4.4 Disadvantages of MANETS
Whilst there are many key advantages to MANETs such as the high mobility of the model, the cost
factors, as well as the ongoing costs, it is not without some downfalls.
One of the biggest disadvantages of MANETs is the difficulty to implement Quality of Service (QoS).
Due to the bandwidth constraint and the dynamic topology of MANETs, supporting QoS is a very
challenging task. QoS is known as ‘a feature of routers and switches which prioritizes traffic so that
more important traffic can pass first. The result is a performance improvement for critical network
traffics’. As one can assume, QoS is a requirement when dealing with detrimental systems such as in
military applications, thus a QoS model is desirable. Recently, because of the rising popularity of
multimedia applications and potential commercial usage of MANETs, QoS support in MANETs has
become an unavoidable task and point of research. Due to the scope of this paper we will not be
reviewing the current approaches, but it is important to note that a lot of work has been done in
supporting QoS across the Internet, but unfortunately none of them can be directly used in MANETs
because of the bandwidth constraints and the dynamic network topology nature of MANETs. [15]
Another key disadvantage of MANETs is the increase in application latency. [16] Due to the wireless
nature of MANETs, latency is to be involved in some form or another. Latency is essentially ‘the
amount of time it takes a packet to travel from source to destination. Together, latency and
bandwidth define the speed and capacity of a network’. [17] We have already defined a MANET as
being a usually low bandwidth network, with the included impact of high latency due to the wireless
nature of the network, the capacity and speed of the network is also going to be fairly low (explained
further below). The increase in this latency will have a direct impact on applications that are run on
the network. This can have a bad impact depending on the application. A very common example of a
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latency sensitive application is multimedia applications such as Voice Over IP (VOIP). This application
requires low latency as the packets containing the voice audio data/possible video data needs to be
forwarded with as minimal delay as possible to ensure fluid communication.
Another key disadvantage with MANETs comes in the form of security. MANETs are generally more
prone to physical security threats in comparison to a fixed, structured, hardwired network. There do
exist entry-level security techniques in place (i.e. encryption) to reduce these threats. That being
said, there is still an absence of link-level encryption at the network layer (Layer 3) within MANETs.
[18] Within a MANET, there are multiple entry points into the network at every node. This makes the
attempt to break into a MANET much easier and without the correct level of security throughout the
network; MANETs can be a very exposed area for attackers.
Lastly, there is the issue that stems the initiative of this research. That is the question on whether or
not ad hoc networks can run standardised protocols on them that are usually used within an
infrastructure network. The scope of this research focuses specifically on the use of routing
protocols (OSPF) on a MANET.
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2.4 Network Routing and Routing Protocols/Algorithms
Routing, within the context of packet data networks focuses on utilizing the most efficient path of
forwarding a packet within a network. Routing devices are typically what form the backbone of a
network. They determine the structure of a network and have control over what packets go where
throughout a network. Wide Area Networks (WANs) are a formation of multiple Local Area Networks
(LANs). With the increasing amount of LANs within a WAN, it is important to use protocols that are
suitable for the network to ensure reliability, redundancy, uptime and overall performance. Typical
routing protocols include RIP, OSPF, EIGRP and BGP. A router uses a routing table to determine
where to send packets. The routing table consists of a set of routes that describe which gateway or
interface the router uses to reach a specified network. This table will initially only contain the
addresses of directly connected networks. To communicate with other networks on the WAN,
routers must be either specified in the table (by the means of static routing), or dynamically added
to the routing table (via the means of a routing algorithm). The routing algorithms mentioned above
are methods of dynamic routing algorithms/protocols.
It is important to note at this point that dynamic routing protocols rely on the routing tables of each
router. The routing table of each router contains vital information for a routing infrastructure. The
information that is included within a routing table is participating networks, routing protocol used,
source of networks, next hop and next hop metric. Each of these pieces of information are used by
the router to determine the best path for packets to travel on the network. [19]
Due to the relevance, the remainder of this section will focus on the Open Shortest Path First (OSPF)
routing protocol.
2.4.1 What is a Router?
It is important at this stage to define exactly what a router is and what its function is. As previously
discussed, routing deals with network addresses, and thus the Network layer (Layer 3) of the OSI
model.
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A routers primary function is to forward packets between devices and networks. A router is simply a
computer running code that determines how and where to forward packets bound for other
networks/devices. The computer that deals with forwarding these packets may be a single purpose
computer with a specialist operating system, or be simulated through a piece of software. [20]
2.4.2 What is OSPF?
The Open Shortest Path First (OSPF) protocol is an Interior Gateway Routing Protocol (IGRP), based
on Shortest Path First (SPF) or link-state technology. It utilizes SFP to route the most efficient
destination of packets. [21] OSPF was designed specifically for the TCP/IP Internet environment, and
supports the following features:

Authentication of routing updates.

Tagging of externally derived routes.

Fast response to topology changes with low overhead.

Load sharing over meshed links.
OSPF also has other mechanisms that allow the network to run more efficiently. One of these
mechanisms is OSPF’s ability to divide the network into ‘areas’. These areas allow the grouping of
certain routers within a network. These areas can determine the logical and physical grouping of
devices within a network. [22] For example, in an office environment, which includes a multitude of
departments, it might be wise to group each of the departments into separate ‘areas’ on the
network.
2.4.2.1 How does OSPF work
There is some terminology that needs to be explained before going into detail of how the OSPF
routing protocol works. Key terms that are required to know include:

Router ID – In OSPF this is a unique 32bit number assigned to each router.

Neighbour Routers – Two routers with a common link that can talk to each other.
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
Adjacency – A two-way relationship between two neighbours.

LSA – Link State Advertisements are flooded; they describe routes within a given link.

Hello Protocol – This is how routers on a network determine their neighbours and form LSAs.

Area – A hierarchy. A set of routers that exchange LSAs with others in the same area. Areas
limit LSAs and encourage aggregate routers.
As previously mentioned, OSPF is a link-state routing protocol. Link state routing protocols can be
though of as holding/generating a distributed map of the network. To get this information
distributed, OSPF does three main things.
First of all, when a router running OSPF is connected and enabled on a network, it will initially send
hello packets to discover its neighbours on the network and elect a designated router (DR). These
hello packets that are sent include link state information, as well as a list of neighbours. Providing
information about the neighbour to that neighbour router serves as an ACK (Acknowledgement),
and proves that the communication between the two routers is bi-directional. It is important to note
that OSPF is smart about the Layer 2 network topology. If it sees a point-to-point link it will know
that this is enough and the link is considered ‘up’. If there is a broadcast link, the router must wait
for an election before deciding if the link is operational. Keeping in mind that a broadcast is a
method of sending a signal where multiple parties may hear a single sender versus a point to point
where a message is transmitted only from one device to another. [23]
The election ballet can be stuffed, with a Priority ID, so that one can ensure the best route is the DR.
Otherwise the largest IP address wins the DR. The key idea with DR and backup DR (BDR) is that they
are the routes to generate LSAs, and they must do database exchanges with other routers in the
subnet. Non-DRs form adjacencies with the DR. The whole DR/BDR concept is used to keep the OSPF
protocol scalable. The only way to ensure that all routers have the same information is to make then
synchronize their databases. If there were 21 routers, and want to bring another one up on the
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network, then 21 new adjacencies would need to be formed. If the database is centralized, with a
backup (just in case), then adding more becomes easy to manage a linear problem. [24]
The database exchange between routers is part of bringing up adjacencies after the hello packets are
exchanged. This stage is very important as if the databases are out of sync; there is a risk of routing
loops and black holes in the network amongst other issues. The last part of bringing up an adjacent
in the network is Reliable Flooding, or LSA exchange. [24]
The full details of an LSA are not required for this research, but it is important to note the
association with areas within the network. Areas were described previously, but one of the key
pieces of information needed to know with OSPF is that Area 0 is a special area, and that if there are
other areas on the network, they all need to ‘touch’ Area 0. Area 0 is known as the ‘Backbone Area’.
There are different types of areas in OSPF, which can become very complex once Virtual Links and
other techniques are added to ensure all areas within an OSPF network touch Area 0.
The final notes that should be taken from an overall overview of OSPF is: [24]

OSPF is a fast-converging, link-state IGP

OSPF forms adjacencies with neighbours and shares information via the DR and BDR using
Link State Advertisements.

Areas in OSPF are used to limit LSAs and summarize routes. Everyone connects to area 0, the
backbone area.
2.4.3 MANET Routing Protocols
It is important at this point to note an overview of ad hoc routing principals and how they differ from
conventional routing techniques as explained previously in the overview of OSPF. Some of the
challenges with routing in an ad hoc environment, as well as an overview of the basic ad hoc routing
techniques will be given in the following section.
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2.4.3.1 Ad Hoc Routing Challenges
There are many challenges faced when finding a routing protocol that will best suit an ad hoc
network. Many ad hoc networks are designed in different ways using different devices and
structures. While each network may be different in some respects, the underlying principals of ad
hoc/mobile ad hoc networks remain the same, with each having similar or the same challenges.
Some of these challenges include: [25]

Dynamic Topologies – With network topologies of structured networks remaining the same
or similar for extended periods of time, routing protocols for structured networks need not
quick update times for when nodes change/structure of the network changes. This poses a
challenge for ad hoc networks where nodes and structure of the network is constantly
changing.

Bandwidth-constrained, variable capacity links – Link speeds for ad hoc networks/MANETs
rely solely on the types of devices and the environmental constraints of where the network
is being set up. Certain environments and devices do not allow for the ranges of bandwidth
and capacity that structured networks gain with wired links (i.e. Ethernet 100-1000Mbps
versus Radio Link @ 2-5Kbps). This presents another large challenge in routing protocols
having a low overhead so the bandwidth available is consumed by the applications required
on the network (i.e. Radio/Video signals in a battlefield).

Energy-constrained – Similar to a bandwidth constraint, energy constrains are posed on the
devices themselves of how much processing power will be required for such routing
protocols. Devices themselves (especially on a MANET) are not normally highly powerful,
with most of the processing power of the devices going, again, into the applications that are
required for use on the network, rather than the routing algorithm/protocol. This poses a
challenge in the respect that the routing protocol cannot be highly processor intensive.

Limited Physical security – As described earlier in the Chapter, physical security of ad hoc
networks is very limited on the grounds that the connections are completely wireless and
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advertised (for the most part). There are only a few precautionary measures that can be
taken in regards to security, and unfortunately not at every level (as described in Section
2.3.4.4).

Scalability – Lastly, scalability poses another great challenge for ad hoc network routing
protocols. This is due to the fact that routing protocol processing and overhead seemingly
gets greater as the network gets more complex. The limitations of the OSPF routing in
regards to scalability were briefly explained in Section 2.4.2.1. The use of areas and other
mechanisms such as DR and BDRs were how OSPF dealt with scalability and upkeep of
reliability and performance. This poses a greater challenge for ad hoc routing protocols as
there is even less room for such mechanisms with lower bandwidth and limitations on
security and energy.
2.4.3.2 Proactive Routing Protocols
Depending on when the route is computed, routing protocols can be split into two categories;
precomputed (proactive) and on-demand (reactive) protocols. This section will describe
precomputed/proactive routing principals.
Precomputed routing is also referred to as table driven routing. [26] In this method, each of the
routes to all destinations are computed in advanced. In order for this to happen, nodes of a network
need to store the entire or partial link state information and network topology information. In order
to keep this information up to date, nodes need to update their information periodically or when a
link status or network topology has changed.
This comes with its share of advantages and disadvantages. A key advantage of proactive routing
protocols is that when a source needs to send packets to a destination, the route is already
available; therefore there is no latency. The disadvantage to this approach is that some routes may
never be used, provided there is always a better/cheaper/more efficient route available. Another
key issue with this in respect to an ad hoc network is that the dissemination of routing information
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will consume a lot of the scarce network resources when the network topology/link state status
changes (this is even more apparent on a MANET). OSPF and other Link State Routing algorithms are
examples of proactive routing techniques. [27]
2.4.3.3 On-Demand or Reactive Routing Protocols
On-demand routing is also referred to as reactive routing. In this type of routing protocol, the route
to a destination node may not yet exist in advanced, but be computed only when the route is
needed. The method to this kind of routing protocol is as follows.
When a source needs to send packets to a destination, in finds a route or several routes to the
destination. This is called ‘route discovery’. After the routes are discovered, the source transmits the
packets across the routes. During this transmission process, the packets may be broken as the nodes
on the route may move or go down. Thus, the broken route needs to be rebuilt. The process of
detecting a break in a route and rebuilding a path to the destination is referred to as ‘route
maintenance’. [27]
The major advantage of on-demand routing is the scarce network resources of ad hoc/mobile ad hoc
networks is greatly saved as the amount of routing information exchanged in maintaining routes is
only to and from those that are forwarding traffic. This kind of approach also removes the need to
constantly update routing information across the network, or flooding the network every time a link
state changes. The biggest fall-back of on-demand routing comes in the form of large latency at the
beginning of the transmission caused by ‘route discovery’. [27]
2.4.3.4 Flooding
Aside from Proactive and Reactive routing protocols, there is another routing mechanism referred to
as flooding. Flooding is the most basic and easiest method of routing, as it requires no knowledge of
the network topology at all. The basic principle of flooding is no route will be discovered or
computed. A packet is broadcast to all nodes on a network with the expectation that at least one
copy of the packet will reach the destination node. Under a light traffic load, flooding can be
Page 25
reasonable robust. However, as one can imagine, the more nodes on a network and the more traffic
that is sent, flooding has difficulty reaching any reliability or efficiency. [27]
2.4.4 Routing Overheads
To provide a method of measuring the performance of a routing protocol in the scope of this
research, this section will go into detail defining what routing overheads are, and what routing
overheads are a good form of measuring the performance of a protocol on a network (i.e. metrics).
An application or protocol, which transfers data across a network, cannot expect to use the full
bandwidth of the communications medium. Along with the application’s data, the communications
protocols transmit information of their own which is referred to as ‘overhead’. [28]
The following section will go into detail of commonly discussed and researched metrics of routing
performance measurements as well as the influences on routing overhead in mobile ad hoc
networks.
2.4.4.1 Routing Overheads – Metrics
This section is dedicated to the metrics that can be used as performance measurements of routing
algorithms. Each of these metrics are commonly discussed in other research of MANET overheads.
Routing Message Overhead
Routing message overhead is calculated as the total number of control packets that have been
transmitted. An increase in the amount of routing message packets that have been transmitted
across a network will reduce the performance of an ad hoc network as it consumes portions of
available bandwidth from the network. [29] This makes the routing message overhead a very good
performance measure of routing overhead.
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Average End to End Delay
A network’s end-to-end delay is defined as the time interval between the generation and the
successful delivery of data packets for all nodes in a network. This end to end delay can be a very
good measurement of network performance as it gives an idea of how well structured the network is
and the efficiency/performance that the routing algorithm has in reducing the latency of a packet
being sent across the network.
Throughput
A network’s need to end throughput is a measurement of the networks successful transmission rate.
It is usually defined as the number of data packets that have been successfully delivered to their final
destination per unit of time. This is another very useful form of measuring the performances of a
routing protocol as throughput can be used to determine the data that the routing algorithm itself is
using on a particular link of the network at any given time t. This allows a thorough check of the
impact of just the routing algorithm on its own, as well as the impact the routing algorithm may have
with other traffic on the network. [30]
2.4.4.2 Routing Overheads – Influences
This section is dedicated to the network variables that have an influence on the routing overheads
and the metrics described above. Each of these variables is commonly discussed in other research of
MANET overheads. [31]
Number of Nodes
The first of the influences is the number of nodes on a network. This can have an effect on how
routing overheads are within a MANET due to the amount of route request packets that are flooded
on a network. The more nodes will have an effect on how many of these packets flood the network.
[32]
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Link Speed
Link speed has a direct relation with routing overheads due to bottlenecks on the network. A very
low link speed does not allow a lot of traffic through, thus creating a larger bottleneck in the flood of
packets on the network. [33]
Movement/Routing Exposure
The frequency of movement and topology changes within the network also can affect the
performance of a network. [34] This should be seen as a major overhead within a network, as the
network topology change will require the recalculation of all nodes within the network, consuming
resources and requiring reconvergence of the routing protocol.
Traffic Loads
According to [35] the traffic load increase may have either a negative or a positive impact on the
routing overhead. Dependent on the routing protocol, the overhead actually decreased with an
increase in traffic load. This makes a good influence to be tested when analysing the metrics of
particular routing algorithm.
Summary Routes
Route summarization can be described as the shortening of subnet masks to include several smaller
networks into one larger network address. As the network grows larger, the number of individual
networks listed in the IP route table becomes too big for routers to handle effectively. They get
slower, drop packets and even crash. Summary Routes are therefore desirable for efficient routing of
a large amount of routes on a network. [36]
2.4.5 OSPF on Ad Hoc Networks/MANETs
Now that all of the basics of networking, OSPF, ad hoc networking as well as routing algorithm
limitations, metrics and influences have been explained this section will go into detail finding any
previous works of a link state routing algorithm such as OSPF on ad hoc/MANETs. It can be
established that there have already been many papers with partial or introduced OSPF routing to ad
Page 28
hoc networking [37] [38] [39]. Some of these developments try and tackle the difficult task of
implementing a structured/link state routing algorithm on an ad hoc network with either no testing
or varying degrees of success.
It is important to note that there are many complications with an implementation of OSPF on ad
hoc/mobile ad hoc networks. We have discussed a lot of these in the previous section(s). While
there are many compelling reasons to not use OSPF on an ad hoc network (such as the problem of
dynamic topologies with proactive routing explained in Section 2.4.3.2), there are also many
compelling reasons as outlined in [37]. OSPF has a very robust backing as it has been around for well
over a decade. The convergence time of OSPF is also relatively quick and it is a fairly lightweight
routing protocol when comparing to other link state technologies. OSPF is also a very well known
industry wide routing protocol. This availability and proven backing gives very promising future in
industry and the use of (mobile) ad hoc networks more frequently.
OSPF offers great integration of multi-hop wireless networking in the existing infrastructure, and
seamless unification of wired and wireless IP networking under a single routing solution. This gives a
further incentive in regards to flexibility, maintenance and costs. [40]
Each of the papers researched have a uniform requirement of any possible extensions to having an
OSPF solution running on an ad hoc network. Each paper [38][39] calls for interoperability. This
should allow the protocol to support wire line networks as well as wireless in the case of a ‘plug in’.
The second common motivation for OSPF to have a MANET extension is the support and the
widespread support of the routing algorithm. This allows a strong basis of experience and skills from
which to work on. A well known protocol can be extended rather than developed from scratch.
One of the most compelling extensions to OSFP comes in the form of an Experimental RFC 5614. This
RFC goes into detail describing the initial issues with OSPF regarding scaling and flooding operation
of the routing algorithm. There is also interesting information uncovered in regards to the
Designated Router election policy (see Section 2.4.2) not being able to converge in all scenarios. The
Page 29
protocol is officially known as OSPF-MDR (OSPF-MANET Designated Routers). The key differences
and extensions that this modified OSPF routing algorithm make is the utilization of DRs/BDRs feature
of OSPF and treating the DRs as a default gateway. [41] The inter-area node is referred to as the
MANET Designated Router (MDR), along with a backup DR known as the BMDR. The MDR is
responsible for flooding LSA packets, via gathering adjacencies formed, to form the whole network
topology. To further help reduce routing overheads, the MDRs can be declared as a non-flooding
MDR to reduce LSA updates (see Section 2.4.4.1).
A further extension to help combat routing overhead is in the adjacency formation process of OSPF.
The normal process in OSFP utilizes hello packets when forming adjacencies with neighbour nodes.
The extension provided in OSPF-MDR differentiates the neighbour relationships with adjacent
nodes. This influences whether the node is routable/full connectivity is plausible between the nodes.
The neighbourhood relationships include Down, One-Way, Dependent, Selected Advertised
(included in LSA) and Bidirectional. [41]
The OSPF-MDR extension shows lots of potential, but lacks in any further development, testing and
use in the real world. Anything beyond theoretical and experimental development has yet to be
done.
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2.5 Battlefield Variables and Limitations of Communications
There is a need to understand the tactical operating environment in order to appreciate the
characteristics in deploying robust communication networks in the field. There are many key
challenges with setting up a network in certain environments, and battlefield variables and
limitations host one of the most difficult environments to successfully set up a tactical network
abroad.
The following section will cover the common fall-backs to the tactical battlefield operating
environment in respect to setting up a communications network.
2.5.1 Limited Bandwidth and Latency
The bandwidth of a tactical communication network is dependant on what the communication
media can support. If the most stringent communication media is adopted, there is a need to endure
that the network configuration is able to support required applications with a low data rate. There
are a number of factors that need to be taken into consideration, especially with the kinds of data
sent across the network to reduce overhead and up keeping a reliable and usable connection of
nodes. [5]
2.5.2 Intermittent Communication Links
Due to the high mobility of tactical nodes, communication links may be broken due to terrain
masking. Networked nodes may therefore appear online and offline intermittently, indicating that
the communication links are unstable and unreliable. [5] This is one of the key issues that will need
to be dealt with at the routing and application layers in a network. This will be further described
later in the literature review.
2.5.3 Hidden Nodes
The hidden node problem is one of the most common issues with wireless/mobile ad hoc networks.
The basis of the hidden node problem can be seen in Figure 1 below.
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Figure 2 - Hidden Node Problem [3]
If node A wants to transmit data to node B, by only sensing the medium, node A will not be able to
hear transmissions by any node in the greyed area (in this case node C). Node A will therefore start
transmitting, leading to collisions at node B. [3] This requires collision avoidance mechanisms such as
using a random carrier sensing timer before data transmission and capturing uni-directional
communications can help to overcome the hidden node problem. [4]
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2.6 Network Simulation Tools
In the area of networking, it can be very costly to deploy a complete test bed containing multiple
networked computers, devices, routers and data links just to validate, verify and/or evaluate a
certain network protocol or network design. It is thus in the interest of network engineers and
researchers alike to find another medium to perform tests and evaluations on without stepping up
to the full scale network implementation just for testing purposes. The solution comes in the form of
network simulators. Network simulators are used in these circumstances and save a lot of time and
money in accomplishing these tasks. [42]
The following section will go into detail in describing what a network simulation tool provides, and a
review of the current most prevalent tools available on the market today; namely, NS2/NS3 and
OPNET.
2.6.1 What is a Network Simulation Tool?
A network simulation tools is an application that allows the technique of implementing a network
within a computer software package. Through this platform, the behaviour of the network is
calculated either by network entities interconnection through mathematical formulas, or by
capturing and playing back observations from a production network. [43]
Network simulators allow researchers to simulate and design networks/protocols from their own
computer and give accurate results that should be relatable and reflected if those parameters are
used in the real world. This gives a much cheaper alternative when testing networks of great
complexity, large environmental challenges, and/or protocols/applications in early stages of
development. [42]
Network simulation tools range from complex to simple as well as open source to commercial.
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2.6.1.1 Commercial and Open Source Simulators
Some network simulators are commercially available products. That means that the source code of
those software packages is not available to the public. Open source network simulation tools on the
other hand are completely available to the public for free use. Their source code is available to
anyone and there are no limitations to the expansions or use of the source code. However, each
type of simulator comes with its share of advantages and disadvantages.
When looking at an advantage of a commercial simulator, the advantage is that it generally has
complete and up-to-date documentation, which is consistently maintained by specialised staff within
the development company. When comparing this to an open source approach, the open source
solution can come as a disadvantage due to not enough specialised people working on the
documentation of the software. The problem can be made even more prevalent when new versions
of the software come out and there is a lack of documentation of the changes made due to difficult
to trace code without any previous documentation. [43]
That being said, the open source network simulator has an advantage in the respect that everything
is open and available so that anyone/any organisation can contribute to the application and find
bugs in it/make changes to improve it. It can also be far more flexible and easy to develop on
regarding new technologies than commercially available software. [43]
2.6.1.2 Simple versus Complex Simulators
There are lots of network simulators available currently both on the market commercially, as well as
online and open source. Minimally, a network simulator should enable users to represent a network
topology, define the scenarios, specifying nodes on the network, the links between those nodes and
the traffic between those nodes. More complex system may allow the user to further specify
everything about the protocols used to process network traffic, in depth device configuration, and
sometimes even the ability to specify and define customized device and/or protocols/applications on
the network.
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Network simulation tools can be further separated into being either graphical or text based.
Graphical applications allow their users to visualise the workings of their simulated network
environment, while text based applications give less visuals/no visuals of the workings of the
network. [42]
2.6.2 Network Simulator 2 and 3
Network Simulator (NS) is one of the most commonly and well-known simulation tools when it
comes to networking research. It is an open source network simulator that has its origins in the REAL
network simulator. The first version of NS was developed in 1989 and has evolved a lot over the past
few years. NS2 is by far the most developed and used version, with many academic papers using NS2
as the simulation test bed. There have been lots of extensions to NS2, with support for a multitude
of networking technologies, protocols and devices. Network Simulator is an object-oriented, discrete
event driven network simulator that uses C++ and OTcl (Tcl script language with Object-oriented
extensions developed at MIT).
Network Simulator has proven efficiency with the backend of its C++ allowing for ultimate efficiency
in simulation scenarios due to the separation of control path implementations from the data path
implementations. That said, while NS2/3 are very efficient platforms to simulate a network upon,
they are very difficult to easily change parameters and initiate a large-scale network topology due to
the fact all events and devices need to be hand coded. There are extensions for a graphical interface
to interact with the tool, but due to the nature of C++, a graphical interface is very primitive, buggy
and does not allow a lot of much needed options for setting up a complex network. [44]
2.6.3 OPNET Simulator
OPNET is one of the most common and popular commercially available network simulation tools
available. Because of how long the simulator has been around and its use in the industry, it has
developed a very good reputation, support base and market share. OPNET has a specialised software
environment developed specifically for networking research and development. OPNET provides the
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user with a powerful GUI and tremendous support for networking devices and protocols. This makes
OPNET one of the most comprehensive and complete networking tools available to this date.
The tool is split into three main functions; modelling, simulating and analysis. As stated before, for
modelling it provides a powerful and complete GUI allowing the user to graphically create a network
topology of their desire. [45] For simulating, OPNET uses three different advanced simulation
technologies and can be used to address a wide range of studies. Lastly, analysis is the collation of all
the data from simulated scenarios on the system and presented intuitively and graphically to the
user in graphical or tabulated formats.
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2.7 Conclusion
In conclusion to the literature review, the concepts of military structure, the importance of Army
rankings and environmental variables in the battlefield were covered in the first section. We find
that whilst the army is a structured organisation, the working conditions and environments may
require restructure and give a strong element of unpredictability. The concepts of networking and
structured networks have been outlined in Section 2.2 and 2.3. Whilst structured networks are
desirable for perfect environmental situations where by there are next to no variables limiting
network infrastructure, ad hoc networks are certainly more desirable when it comes to limiting
environments and unpredictable situations. In regards to the military’s use, MANETs are certainly
desirable due to the flexibility, highly mobile nature and the ease of configuration MANETs offer.
Routing is one of the most important elements of networking. Routing is the backbone of all
networking communications. It determines what packets of data go where, allowing the connection
between devices in wide area networks. While MANETs have an inherent advantage in complicated
environments, they have difficulty supporting a routing algorithm that will maintain reliability and
efficiency across the network. OSPF is one of the most prevalent, used and mature routing protocols
available today. It has many features and benefits that would be desirable for use on a MANET. As
found in literature, routing overheads caused by flooding is one of the most prevalent issues with
OSPF, but little formal testing has been performed using OSPF in a military MANET environment.
There have been plenty of suggestions in the form of RFCs in extending OSPF for better use on a
MANET, but none have been tested to determine the real overhead of OSPF in such an environment.
Network simulators are one of the best ways to test complicated network topologies and
technologies in a cheap and accurate manner. There have been no accounted tests using either real
world implementation or network simulation of OSPF on a MANET of limited environmental and
device circumstances.
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Due to this gap in the research, the proposed research question is “Can OSPF be used to efficiently
support a military MANET under limited conditions such as low bandwidth, high drop outs, and unit
mobility?”
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Chapter 3 – Methodology
In Chapter 2 it was shown that the use of OSPF in military MANETs has been avoided due to
concerns with the routing protocol’s performance and reliability on ad hoc networks. However, the
use of custom routing protocols for ad hoc networks is also difficult to implement due to their lack of
formal implementation and/or testing. As such the research question in thesis is as follows:
“Can OSPF be used to efficiently support a military MANET under limited conditions such as low
bandwidth, high drop outs, and unit mobility?”
To address this question the following research method will be applied.
The chapter is structured as follows.

The commonly used mythologies will be firstly covered to determine the best approach for
this type of research.

The Research Strategy/System development section of the methodology will outline the
method of developing topologies from common military structures that will most accurately
represent the said structures in a mobile ad hoc network environment.

The Research Validation/Evaluation section of the methodology will outline what occurred
with the simulation. This includes the configuration of the simulations parameters and what
parameters will need to be extracted and evaluated upon.
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3.1 Commonly used Methodologies in Research
The methodology that will be used in this chapter to address the research question is based on
previous work by Crnkovic [46]. He suggests that a question is first chosen regarding the research,
and then a result is extracted via a particular strategy and validation technique. For each stage he
suggests five different types of research questions, which have been summarised in Table 1. An
example of a type of question that is being proposed is “Does X exist and what is it?” A strategy is
then selected to provide an answer to the question. In this case it could be any of the five as seen in
the middle column of Table 1. The final stage is selecting a validation technique to verify the results
from the strategy stage. The selected validation technique relies on the strategy used.
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Table 1 - A research methodology suggested by Crnkovic [46]
Question
Strategy/Result
Validation
Qualitative model
Feasibility
Report interesting
Persuasion
Does X exist and what is it?
observations
I thought hard about this, and I
Is it possible to do X at all?
Generalise from examples
believe . . .
Structure a problem area
Characterisation
Technique
What are the characteristics of
Invent new ways to do some
X?
Implementation
tasks, including
What exactly do we mean by
Here is a prototype of a system
implementation techniques
X?
that . .
Develop ways to select from
What are the varieties of X and
alternatives
how are they related?
Method/means
System
How can we do X?
Embody result in a system
Evaluation
What is a better way to do X?
using the system both for
Given these criteria, the object
How can we automate doing
insight and as a carrier of
rates as . .
X?
results
Generalisation
Empirical model
Analysis
Is X always true of Y?
Develop empirical predictive
Given the facts, here are the
Given X, what will Y be?
models from observed data
consequences
Selection
Analytic model
Experience
How do I decide whether X or
Develop structural models that
Y?
permit formal analysis
Report on use in practise
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In this research, the methodology has been separated into two sections as per Crnkovic’s model.
Referring back to Table 1, the chosen best fit for the question posed is Feasibility. The next step is
choosing a strategy of best fit from the second column of the table. In this case, the best fit is
System. This is due to there being no reliable findings in the literature that directs us further to
results according to the posed question of the possibility of OSPF running on a MANET. Lastly, as the
Validation stage relates directly to the Strategy/Results the chosen Validation is Evaluation. This
includes the evaluation of some form of model or test from a built system to determine whether or
not OSPF will run on a military MANET.
The following Table 2 will accurately reflect the research methodology that has been adapted from
Crnkovic’s model, with the Question, Strategy/Result and Validation sections relevant to this
research.
Table 2 - Adapted Research Methodology
Question
Strategy/Result
Validation
System
Evaluation
Develop a system that will
Assess the outputs from the
accurately represent a military
Feasibility
system upon running each of
MANET environment.
“Can OSPF be used to
the cases and scenarios.
Develop network cases and
efficiently support a military
Conclude using the
scenarios to represent the
MANET under limited
performance metrics of OSPF
military’s use on such a
conditions such as low
to confirm whether OSPF is a
MANET system.
bandwidth, high drop outs,
viable routing protocol for use
Run OSPF on this system and
and unit mobility?”
on a military MANET.
these cases/scenarios and
gather the outputs of the
performance metrics of OSPF.
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3.2 Research Strategy - System
We need establish a method of gaining meaningful results that will allow us to confirm whether
OSPF will work on a military MANET. The first step in the Strategy/Result phase of the methodology
will require a means of developing a system upon which the theory can be tested in answering the
initial question. This strategy phase can be broken down into a multitude of steps as outlined in the
following section.
3.2.1 Understanding Hierarchy Military Structure
This phase of the methodology required a thorough investigation of the military structure to gain
understanding into the type of system that would be developed and engineered to best fit the
application of a MANET in the field of battle. This extensive research will be undertaken through
open discussions with DST Group staff member who present the most relevant, up-to-date, and used
communication structures.
The desired output of this activity is a series of military standard (MILSTD) drawings that accurately
represent the communications network and structure of the military personnel/units associated
with the network at hand.
3.2.2 Developing Network Topologies
The next phase of the Strategy part of the methodology will require network topologies to be
developed as a commencement of the network systems development phase. These network
topologies will be developed to accurately represent the outcome of the previous stage, with close
interactions with the DST Group to ensure that each topology is accurate to the real world
communication network scenario. The development of these network topologies will also require
the specific rules of OSPF to be adhered to. A simple example of a Network Topology is a basic
network comprising of three routers connected via Ethernet running OSPF as a routing protocol.
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Figure 3 – A Basic Network Topology
3.2.3 Developing Network Scenarios
The next phase of the Strategy part of the methodology is the development of network scenarios.
Each of the network scenarios are required to be designed to run upon the topologies developed in
the previous phase. The scenarios are also required to accurately show the significant situations that
these military MANETs will experience to test the effectiveness of OSPF as a routing protocol. These
situations will be developed closely with the DST Group as per requested to ensure the situations
being represented are accurate to those that the MANETs will experience in the field during
operation. A simple example of a Network Case for the previously explained basic network topology
in Figure 3 is a case where one of the routers links fail to the other router. In this case we could
suggest the link between R1 to R3 failing.
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3.3 Research Validation - Evaluation
The second main section of the methodology for this research is in the Validation phase. As in Table
1, it has been chosen to develop a System for the Strategy/Result phase. This leads directly into the
Validation phase of Evaluation. Evaluation can be extracted as ‘Given these criteria, the object rates
as…’ This can be further converted for use in the case of this research as the phase of evaluating the
network cases and scenarios to determine the overall impact of OSFP on such a system. For this
evaluation to occur, the following steps are taken.
3.3.1 Network Topologies and Cases to a System
This step requires the developed network cases to be run on networks that have been setup as
according to the network topologies/systems as previously described. The method of setup of these
networks will be covered in more detail in the further on. The desired outcome of this step is
successfully converting the topologies and cases to a system to evaluate upon. Once the cases and
topologies have been successfully converted a system, the inputs will be determined for the system
as follows.
3.3.2 Determine Inputs for the System
This step of the Evaluation phase requires the determination of the inputs for the system prior to
running these simulations. These inputs will need to be consistent across all network topologies and
scenarios, as they will be compared to each other. Inputs may include failure models to determine
how OSPF reacts to a node dropping out, or packet size and rate, link speeds and connections,
device types and setups, as well as possible simulated traffic on the network. The desired outcome
of this step is determining all of the hard line requirement variables that will be run on each scenario
and topology.
3.3.3 Determine Outputs (metrics) of System
The next step of the Evaluation phase requires the determination of the outputs of the system after
running the simulations. These are the metrics that we desire to use to evaluate the actual
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performance of the OSPF routing protocol. This was previously touched on in Section 2.4.4. Each of
these metrics will be used for all of the topologies and cases of the system. The desired outcome of
this step is having a conclusive set of metrics that will accurately be used to represent the
performance of the OSPF routing algorithm.
3.3.4 Make Predictions and run Simulations
This step of the evaluation phase requires the previous knowledge of the OSPF routing algorithm
and making predictions of the protocols effect to being run on such a topology and scenario. These
predictions will be recorded and then the simulations run. The desired outcome of this phase is
recorded predictions for the cases and scenarios inputted to the system, as well as simulation being
run and results recorded and collated.
3.3.5 Draw conclusions from Outputs
The last step of the Evaluation phase is analysing the results from the determined metrics. Once
these results have been compared against all of the other case/topology results, conclusions will be
drawn and predications made against the conclusive evidence given in the outputs.
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3.4 Research Method to Use
This kind of research falls into the category of modelling the behaviour of a network, specifically
modelling the behaviour of a military mobile ad-hoc network when an OSPF network routing
algorithm is used within it. There are two main methods to modelling network behaviour, mainly
full-scale implantation and full system simulation. The following section will briefly explain each
method of network behaviour modelling and the term ‘Network Behaviour’ itself.
3.4.1 Network Behaviour
Network behaviour is the set of observations or measurements that can be made about a network
over time (t). The growth of network-based computing and the Internet have ensured that networks
can no longer be considered in isolation, as events external to a particular network increasingly
impact its behaviour. This set of observations or measures help further understand the impact
certain elements have on a network. In this case, we will be determining the impact OSPF has on a
network type (MANETS) that does not normally utilize OSPF as its routing protocol. Conclusions can
then be made whether or not OSPF is a likely candidate for use on military MANETs.
3.4.2 Full System Implementation
Full-scale implementation is the means of designing and implementing a network of the
specifications required at a full scale in the real world using physical hardware and data links. The
full-scale network in this case would directly represent the network that would be utilized out in the
field. This network would utilize all of the devices and connection as per required and requested by
the client. This includes the physical, data link and network layers (cabling and wireless interfaces,
etc.) as well as the transport, session, presentation and application layers as described in Chapter
2.2.1. The network would then be put through a series of ‘tests’ or ‘cases’ that move traffic
throughout the network in a means that represents how said traffic will move around the network in
the field over a time frame similar or the same as used in the field. The network traffic, devices, and
data links are then analysed by means of network analysis tools such as Wireshark. [47] Through the
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analysis stage the data is put into meaningful results such as graphs and tables to be easily analysed
and compared to other cases.
This method has its share of advantages and disadvantages. The major advantages being the
simulation will be nearly 100% accurate provided it is setup and used exactly as it would be in the
real world. The output of said implementation will also provide complete and accurate results for
analysis purposes. With the tests being run over the same period of time using the same methods of
usage as in the field, the results will directly provide all details associated with OSPF performance, as
well as all other network variables (dropouts due to environmental changes, device failures, network
stability, etc.) throughout the simulation. The obvious disadvantage to this kind of network
behaviour modelling is the cost. Both time and money wise, this method of analysis is very
expensive. The costs are very out of reach for this particular research, and the client itself. As there is
not a lot of current research and analysis on running ‘off the shelf’ OSPF on a MANET, this method
would also be a very risky financial gamble. If the said implementation does work, much of the work
can be easily transferred to the real work implementation as the analysis and research is undertaken
on a full-scale scenario. If said implementation does not work, the full-scale implementation
designed solely around the setup of OSPF on a MANET would be virtually unusable for both future
research and fieldwork.
3.4.3 Full System Simulation
Full system simulation is the means of designing and implementing a network of the specifications
required on a network simulation tool using simulated devices and data links. The network
simulation would also directly represent the network that would be utilized in the field, but has the
advantage of not physically requiring setting up. This network simulation should also utilize all of the
network devices and technologies (such as routing protocols) as required by the network
specification, provided the network simulation tool in use supports them. Similarly to the Full System
Implementation, the network simulation tool would allow us to run the simulated network through a
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series of ‘tests’ or ‘cases’. These tests will move traffic/nodes throughout the network as per
required in the specifications. The network simulation tool records all of the traffic, link and device
information as required within the tool itself. The data can then be meaningfully analysed through
graphs and tables at the end of the simulation.
Again, this method has its own share of advantages and disadvantages. The key advantages being
the cost factor. Using a network simulation tool is much cheaper than setting up an entire network
as the only initial outlay is the network simulation tool itself. The time factor is also greatly reduced,
in comparison to setting up physical devices across a physical landscape. Another advantage is
provided the network simulation tool is trusted and has strong backing/proved accuracy; the results
yielded from said application are truthful to the real world figures. Obviously with such strong
advantages, there is also a share of disadvantages. The main disadvantage being the fact that it is a
simulation, which does not have a guaranteed accuracy to a real world scenario. While the accuracy
may be out, the simulation will provide meaningful results to the scale and accuracy required for this
research. Another disadvantage is in the support for devices and network technologies. The
simulation software needs to provide all of the libraries and models for real world devices and
network technologies such as routing algorithms and network traffic simulation. The key factor that
needs to be fulfilled when using a network simulation tool is choosing the right one. This ties in all of
the statements above including finding a good quality simulation tool that has a strong support and
trust backing it, a support for all required devices and network technologies, as well as a tool that
has the ability to output the required data for analysis.
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3.5 Network Simulation Tools
The only tool that will be utilized throughout this research is OPNET Network Simulator. Each of the
network simulators that is available for use is further described in 2.5. OPNET Network Simulator is
the best-fit tool for this kind of analysis. The simulator has a very intuitive and easy method of
inputting network topologies, which is beneficial with the amount of topologies, and cases that will
be used. OPNET was also chosen as it supports all of the routing protocols required including their
full feature set. This means the simulations will best represent the real world cases as required by
the client. OPNET is also the easiest solution to adopt, as there is no need to learn complex
algorithms and programming languages. All of the devices and other applications such as VOIP are
also available in OPNET Network Simulator. This will also give a better fit from simulation to a real
world implementation. OPNET also integrates all of the data gathering and analysis in a simple and
intuitive way to interpret and compare with other scenarios/cases.
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3.6 Summary
In Chapter 3 it was revealed the initial gap in the literature regarding the use of the OSPF routing
protocol upon a military MANET. This lead onto the research question being formed, “Can OSPF be
used to efficiently support a military MANET under limited conditions such as low bandwidth, high
drop outs, and unit mobility?”. The research methodology was then determined via a means of ‘bestfit’ in reference to Crnkovic’s research methodology. From this a Feasibility, System and Evaluation
methodology was extracted and interpreted for use in answering the initial research question. The
methodology determined the development of a System to assess the performance of the OSPF
routing protocol on a military MANET as if it were in the real world military environment the best
Strategy in answering the research question. This means the OSPF routing protocol is run on a
network simulator throughout a series of cases and scenarios to best represent that of a real world
military MANET in the corresponding environment. The evaluation phase of the methodology would
be in extracting the routing overheads/costs of the OSPF on military MANETs to determine whether
the usage of such a routing algorithm would be feasible in the real world.
Now that the research question and methodology of research has been outlined in Chapter 3,
Chapter 4 – Simulation Design will commence on the Strategy/Result phase of the methodology.
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Chapter 4 – Simulation Design
The following chapter will go into detail of how the network topology and technologies such as OSPF
can be accurately adapted and utilized in such an environment. This will require firstly going into
detail of what a military structure/organization consists of. This includes the overall structure, as
well as the hierarchical connections that each of the soldiers have to connect and communicate with
other levels of the organization. It is important to use the correct terminology and symbology as
briefed by the DST Group. Once the theory of the structure has been concreted, the concepts of
network topologies will be touched on. This will include the main differences between both
structured and dynamic network topologies. Moving on from this comparison we will tie in all of the
learning’s of military structure and network topologies to represent these organizations and
structures in a network topology, which can then be utilized for simulation purposes.
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4.1 Military Structure
To accurately represent a network of military nodes on a network topology we are first given the
task of identifying the structure and organization of the military where the communication
technology will be utilized. This is a required phase of the research, as a network topology cannot be
setup without knowing the key factors such as type of equipment that the network needs, the
capabilities of the equipment, the growth and structure of the network, as well as the way the
network is managed.
Military rankings can be identified into a multitude of different elements of command. These
elements of command are also known as ‘units’. Each unit includes a different name to identify
themselves, as well as different purpose, structure and size. Each of these elements are key factors
in knowing how to describe a scenario in a network topology.
Below are a list and a basic overview of the chain of command common in a military structure. The
following list has been adapted from the United States Army Chain of Command, incorporating key
elements and details given by the Australian Defence, Science and Technology Group adhering to
MILSTD 2525B. [48]
Fire Team
A fire team (also known as a Brick) consists of 2 to 4 soldiers. A fire team is a very mobile unit in the
structure. They are required to be mobile from other elements of the Section and Platoon as they
are sniper/assault teams on the ground.
Section
A section/squad typically contains 8 to 10 soldiers and is commanded by a sergeant or staff sergeant.
This is the smallest element in the Army structure and sits at the bottom of the hierarchy.
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Platoon
A platoon typically consists of 30 to 40 soldiers. It is also known as a Troop and is a culmination of 3
to 4 Sections.
Company
A company has alias names including Combat Team (CT) or Squadron/Battery. A company is the next
level up from a Platoon and typically consists of ~120 soldiers. As with the hierarchical structure of
the military, this is usually a culmination of 3 to 5 platoons. For this research we are under the
assumption that each Company contains exactly 3 Platoons as given by the DST Group.
Battalion
A Battalion (also known as a Battle group (BG) or Regiment) usually consists of ~700 soldiers.
Typically, 4 to 6 companies make up a battalion. For this research we are under the assumption that
a Battalion consists of 3 Companies.
Brigade
A Brigade (also known as a Task Force (TF)) consists of ~4500 soldiers. This is normally made up from
three battalions. This is the highest element in the military structure for the scope of this research.
4.1.1 Military Symbols
Military structure is best and accurately represented via diagrams. Diagrams when explaining
military organization are best shown using MILSTD 2525B. [48] This is a standard that has been
devised over the years and is the internationally recognized standard for representing military
structure diagrammatically. This section will first go into the explanation of the required military
symbols for this research and their meanings, then go into an overview of the military structure that
we will be dealing with.
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Figure 4 – Military Symbols from Axis and Allies Wiki [49]
The Figure 4 above shows the diagrams of each of the hierarchical elements as described in the
previous section. This can be further clarified and condensed in the following Table 3.
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Table 3 - Military Symbols (Detailed)
Hyphenated
Name
BDE
BN
Symbol
Size
Alias
Brigade
4500
Task Force (TF)
Battalion
~700
Battle group
(GB)/Regiment
COY
Company
120
Combat Team
(CT),
Squadron/Battery
PL
Platoon
30-40
Troop
SECT
Section
8-10
Squad
FT
Fire team
2-4
Brick
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Figure 5 - US Army Hierarchy Military Structure [50]
The above Figure 5 accurately represents the military structure that we are dealing with, given in an
overall hierarchical view. For the purpose of this research we will only be dealing up to the Battalion
level as pre requested by the DST Group.
Lastly, the Platforms will be described in the following Table 4. These will only be used to identify
what kind of platforms are in in each of the hierarchical elements in section 4.3.1.
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Table 4 - Military Platforms Identification
Name
Soldier
Soldier Sig
Vehicle
Vehicle CP
(dismounted)
(dismounted)
ID
A
B
C
D
Description
Single Radio
2 Radios or Dual
3 Radios
5 Radios
VHF – UHF
Channel Radio
Single Channel
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4.2 Network Topologies
The following section is provided to give a basic overview of network topologies before we go into
detail in converting the military structure into a set of network topologies that can be used to
accurately represent and simulate upon.
Network topologies are utilized to layout the connection of devices on a network. They act as a
visual aid in how a network will be planned out prior to its implementation. There are many
standard network topologies currently in use in the industry. Each of these network topologies will
be briefly explained to further help understand the design and possible limitations when
representing a military MANET using conventional networking tools and protocols.
4.2.1 Structured Topologies
Structured network topologies are the most commonplace for use in the industry. They can be easily
identified for a particular network’s purpose and adapted for use using one or a combination of the
following topology concepts. There are 5 basic types of network topologies as follows:
Figure 6 – Network Topology Categories [51]
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Bus
Where a single cable (the backbone) functions as a shared communication medium upon which all
devices attach or tap into with an interface connector.
Ring
Every device has exactly two neighbours for communication purposes. All messages travel through a
ring in the same direction.
Star
Star uses a central connection point called a ‘hub node’ that may be a network hub, switch or router.
Hierarchical/Tree
Tree Topologies integrate multiple star topologies together on a bus. This can be represented in a
hierarchical structure where the top node represent the main router, and each of the nodes below
represent the main router for each of the nodes of a department, etc.
Mesh
Concept of routes. Messages sent on a mesh network can take any of several possible paths from
source to destination. Terrific for redundancy purposes.
From the given descriptions and explanations we can identify the most valid and purposeful
topologies by relating back to the previous section on military structure. As the military structure
most relates to the hierarchical/tree network topology concept we will be utilizing this as the basis
development topology of the simulation networks. It is also important to relate the given
requirements by the DST GROUP to these network topology concepts. Importantly, we will be
utilizing elements of the mesh network topology concept to represent the redundancy requirement
as given by the DST GROUP.
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4.2.2 Dynamic Topologies and the Limitations of Structure
To the following section will describe dynamic network topologies and how they can be utilized for
the mobility concept requirement.
As the DST GROUP have provided a requirement for soldiers apart of Platoons to be completely
mobile between other platoons in the Battalion, another concept needs to be defined to answer this
requirement. That concept is Dynamic Networks and the difference they have to structured
topologies.
The main conceptual difference between Structured and Dynamic networks is that networks that are
dynamic have a topology that can change over time. Nodes and or edges may come and go. In
comparison, a structured network is typically concrete and does not change over the lifespan of the
network. This will not entirely suit the MANET requirements, as mobility and environmental changes
are key concepts and the defining features that makes them a valuable asset and fit to the military.
4.2.3 OSPF and Network Structure
It is important at this point to recognise that while OSPF is a dynamic routing protocol, it is usually
utilized in structured and Local Area Networks as setup in a ‘normal’ network environment such as
an office or a school. OSPF shines in its ability to recognize dropouts and other network issues and
rectifying them via dynamic routing in a quick and efficient manner (as described earlier). OSPF
therefore would not typically be thought of as being applicable for such a dynamic and
environmental challenging environment such as that of a military ad hoc network.
That said, there are many reasons that OSPF should be utilized and is conceptually a good fit for this
application. As a proactive link-state routing protocol, OSPF employs periodic exchanges of control
messages to accomplish topology discovery and maintenance. Packets called Hellos are exchanged
locally between neighbour routers to establish bidirectional links, while other packets called LSAs
reporting the current states of these links are flooded throughout the entire network. This signalling
will result in a topology map that is present in each node on the network. This makes the use of
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OSPF on MANETs a very interesting avenue of research as the routing algorithm’s concept provides
itself to be dynamic enough that it will update as changes occur on the MANET. [52]
That said there are some limitations that we need to consider prior to developing these simulation
network topologies that will run and utilize OSPF. Some of these limitations are in the way OSPF is
required to be setup. As previously mentioned, OSPF uses flooding to exchange link-state updates
between routers. Any change in link state information is flooded to all routers in the network. Areas
are a technique used to introduce borders on the explosion of link state updates. As the
requirements of the network are low-bandwidth, we will need to consider the use of areas and
border routers in the network design. This needs to be taken into consideration as the main rule
when setting up areas is that all routers need to be connected (in some capacity) directly to the
router that is area 0 (the main exchange). As we have defined the military organizational structure as
being best suited to a hierarchical network topology, there will be some limitations and possible
adaption of another routing algorithm in the case that the one of the routers (nodes) are not
connected directly to the area 0 router. This can be shown in the following diagram (Figure 7) where
RIP and BGP are utilized on said routers.
Figure 7 –RIP and BGP on Routers Topology [53]
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Possible solutions to such a network design include the use of Virtual Links and/or another routing
algorithm such as RIP or BPG on the routers that are not physically connected to Area 0. The design
decisions will be further outlined in the next sub section 4.3.
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4.3 Representation of Military Structure as a Network Topology/Scenarios
The following section will go through all of the design decisions that were made in representing the
military structure as a network topology to represent the MANETs that will be analysed for the
simulation. This chapter cover the ideology and creation behind developing the network topologies
and scenarios that will be used to simulate, and analyse once transformed into OPNET Simulator.
For the purpose of this paper, the only cases and topologies that will be covered are the main
analysed scenarios; the test cases will not be covered in this paper.
4.3.1 Requirements Provided
At this point it is important to concrete some of the requirements provided by the DST GROUP
before coming up with the test cases for the simulation. The requirements stated by the DST GROUP
include:

Two connections between each hierarchical element (ie. PL to CO, etc) for redundancy
purposes.

Each of the simulations includes all of the soldier nodes represented using provided amount
and structures for each unit/element.

Solider mobility is represented (allowing soldiers to freely move between different
platoons).

OSPF is utilized on ALL network cases as a means of measuring the routing overheads on
network simulations best developed to represent the structure of the military MANETs.
4.3.2 Defining Military Organization
This section will go into detail describing the diagrams that were devised throughout multiple
meetings with DST Group. Each of the diagrams will be described with details that were also given
throughout the meetings in regards to details that may not be directly included on the diagrams
themselves.
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The structure of the following section will go from top-level diagrams down to the bottom level that
will be dealt with in developing network topologies and cases.
4.3.2.1 Top Level MOT BN
The following diagram is the top-level overview of the military organisation that will be using the
MANET system.
Figure 8 - MOT BN
The above Figure 8 represents the overall view of the motorized battalion network that will be
utilizing the MANET. The Battalion network is the highest level that we will be focusing on. Each of
the links to other elements of the military organisation is represented by the links going from one
NET to another. At this stage it is important to note a few things that will be detrimental to the
development of network topologies and network cases. Firstly, it is important to note that there are
always two links between the company network and the battalion network. These two links are
there purely for redundancy purposes. The amount of soldiers internal to the network at this level is
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~700. It is also important to note that a Battalion network includes three Company networks as can
be seen by COYA, COYB and COYC. The next level of the military organisation that we will focus on is
the Company level.
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4.3.2.2 MOT COY
The following diagram is the next level down the chain of command in the military network
hierarchy. This diagram represents the Company networks connected to the Battalion network.
Figure 9 - MOT COY Structure
The diagram shown above (Figure 9) is in MILSTD 2525B. [48] This diagram is used to see both the
structure of the company network, but also where each soldier grouping is located within the
network. In this case, we can see the COY network is made up from ~120 soldiers.
Figure 10 - MOT COY Overview
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Figure 10 represents the company network, but in an overview view. This allows the viewing of each
of the links to the network as the hierarchy ranks up. It is important to note at this level that the
initial requirements are adhered to, of only two links between the ranks. Therefore, only 2 links will
be utilized between the Platoon network and the Company network / Company to Battalion, not the
3 or 4 shown in this diagram. It is also important to note at this stage that the internal workings of
each of the networks does not need to be known for the purpose of this research. Lastly it is
important to note that each Company level includes three Platoons.
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4.3.2.3 PL NET
The following diagrams represent the next level down in the chain of command in the military
network hierarchy. In this case, we will focus on the lowest level that will be overlooked in this
research, the Platoon level.
Figure 11 - INF PL
The diagram above is also in MILSTD 2525B. [48] This diagram is best used to represent the internal
structure of the Platoon network. While in the focus of this research we do not need to focus on the
internal workings of each level hierarchy, it is important to note the amount of overall soldiers in
each network. In this case, there are ~30-40 troops in each PL.
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Figure 12 - Dismount PL Network
As can be seen in Figure 12, the overall view of the Company and Platoon network is shown. It is
important to note in this diagram the SIG connection between the PL and the COY Net. This SIG
actually represents two links by SIG soldiers within the PL network. As in the requirements, these SIG
soldiers represent the dual link redundancy connection for each Platoon to the above hierarchy.
Each of the SECT networks below the Platoon Network are not required in the scale and/or scope of
this research and can be ignored as the soldier count at each network level compensates for these
lower level entities.
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4.3.3 Converting to Network Topologies
The following section will go into detail in the conversion process and design decisions of
transforming the military diagrams into the System phase of the proposal. This section will only be
covering the main cases that were used to extract relevant results from. Test cases will be ignored
for the scope of this paper. The levels will be done from the bottom up for sake of simplicity (i.e.
starting at the bottom level [Platoon Level] and working up to the top level [Battalion Level]).
4.3.3.1 INF Platoon Network
The INF Platoon will be represented by two separate networking topologies. This will allow a more
detailed analysis on at the Platoon/Company level prior to stepping up to a full-scale model that
includes the Battalion network. This design decision was made in conjunction with the DST Group as
the full-scale implementation includes ~700 nodes. The first topology that will be represented is the
more detailed topology at the Platoon and Company level.
Figure 13 - Platoon/Company Detailed Case
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As can be seen in Figure 13, there are only 5 soldiers in total. These soldiers are connected to two
Platoon networks respectively. Each of those Platoon networks is then connected to the Company
networks above. The reason this topology is developed on a much smaller scale than a standard
platoon network (~30-40 soldiers) is this topology was developed as an initial test of mobility. The
small scale of the topology allows us to easily move soldiers between Platoon networks. This comes
as a design decision of OPNET and the DST Group. The DST Group requested an example that
allowed an element of mobility. OPNET enabled this via a Failure model on the links. This allows the
links of soldiers to be failed and restored at time any time ‘t’ throughout the duration of a
simulation, thus, inducing a method of mobility.
Figure 14 – Full Scale PL Network Topology
Figure 13 above shows the simple Platoon network topology. This network topology was decided as
the simple representation of a platoon network as it only includes two physical nodes. This design
decision came after a meeting with the DST Group. It was determined that the internal structure of
the networks was not necessary in a full-scale implementation of the MANET, therefore only the
requested number of soldiers needed representation. The complete representation of ~30-40
soldiers at this level is not required by 30-40 separate nodes, thus the design decision of the use of
Loopback interfaces is used.
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4.3.3.2 Company Level Network
The company level network topology will again be represented by two separate network topologies.
Please refer to section ‘4.3.3.1 Platoon Level Network’ for information about the design decisions
regarding the conversion of the Platoon/Company Detailed Case as per Figure 13.
The full-scale CO level network topology can be represented as follows.
Figure 15 - Full Scale CO Network Topology
This topology was developed to most accurately represent the Company level network. This
topology (Figure 15) shows each of the three Platoon networks. These networks are connected via
dual link SIG Soldiers as per requirements. The dual link SIG Soldiers are also used in the connection
to the Battalion network as required. The design decision was made to have a ‘HUB’ router that acts
as the main router for the Company. This decision came in conjunction with the DST Group, as the
internal network structure did not matter, so long as each solider was accurately represented and
the dual link requirement was retained. This design decision also provides a debugging mechanism
to check routing tables and make sure the network is performing correctly.
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4.3.3.3 Battalion Network
The overall Battalion network will be represented by only one network topology. This is due to the
large scale of the implementation of such a network (~700 soldiers at this level). The Battalion
network is setup similarly to the full scale Company network as can be seen in Figure 16 below.
Figure 16 - Full Scale Battalion Network Topology
As can be seen, this topology was developed with all design requirements adhered to. The dual links
to the CO level networks are retained. The design decision to have a HUB router to control all routes
at this level was made to ensure the correct routes were being relayed throughout the network via
means of debugging with IP routing tables. It is important at this stage to note a key design decision
with the full-scale network topology. The use of network Areas has been made when running OSPF
across the network. This is to help divide the network into the separate Company/Platoon networks.
As this design decision was made, the separation of the network needed to be determined. As each
of the Areas needs to touch Area 0 (See Literature Review – Chapter 2), the design decision was
made to separate the network into Areas 1,2,3 respectively, between the BN and each of the CO
Networks. This created an issue regarding the Platoon networks though, as if they were to run OSPF,
they would not be touching Area 0 without a method of virtual links. The design decision was made
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to use RIP Routing protocol between the Platoon Networks and the Company Networks to alleviate
the need for Virtual Links, and retain the use of OSPF Areas.
4.3.4 Developing Network Cases
The developments of network cases that will be run upon the topologies are outlined in Chapter 5 –
Simulations.
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4.4 Determine Inputs for the System
This section is covered in Chapter 5 – Simulations. This information along with the Development of
Network Cases has been explained at the beginning of each Scenario for clarity of information
regarding each case.
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4.5 Determine Outputs (metrics) for the System
Each of the cases that will be run on the network simulation tool on the network topologies
developed will need to have a standardized set of information extracted and analysed for the results
to be meaningful and comparable. The following section will cover what information will required
extraction from the network simulation tool logs to give conclusive evidence regarding whether or
not OSPF is viable on military MANETs.
To show whether or not OSPF is a viable solution for military MANETs, the overhead and throughput
will be the main focus points of the data collection and analysis. The following headings represent
the data that will be extracted from the simulations. Each of these includes a brief explanation as to
what the data means and why it was chosen for extraction.
4.5.1 IP Forwarding Tables
IP forwarding tables (also known as Routing Tables) are a table that is used to display the routes a
router on a network has. This gives a terrific insight when analysing a network as it shows at any
given point in time what a particular router may or may not have access to. The reason this is
particularly interesting for concluding whether or not OSPF can be used on a MANET is that OSPF
controls how the routing table will react in specific cases as it is the routing algorithm for the
network simulations. This is vital in knowing OSPF’s reaction to cases such as network dropouts, or
mobility, etc.
4.5.2 OSPF Traffic
OSPF Traffic is usually measured in a data per second rate. OSPF traffic represents the amount of
traffic (data packets) at a particular point in time that is being sent or received by the OSPF protocol
in particular. As one of the main features of the MANET is low bandwidth devices and links, this will
be vital information in debunking whether or not OSPF is even viable with the bandwidth capabilities
of the links, and devices in question.
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4.5.3 Point to Point Throughput
Point to point throughput is usually measure in a data per second rate. Point to point throughout is
measured on a particular link in a network topology. It represents the amount of traffic (data
packets) at a particular point in time that is being sent or received over the chosen link in the
network. Again, as one of the main features of a MANET is mobility and low bandwidth, it needs to
be determined whether or not there is too much traffic over a link that exceeds those of the
requirements of the MANET.
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4.6 Summary
The end goal for Chapter 4 was the development of network topologies and cases/scenarios to best
represent the military MANETs in the expected environments. The chapter went into detail in
revealing the important aspects of the military structure and organisation that the MANETs in
question will be utilized for. It was revealed that the military utilize a very hierarchical ranking
system when organising soldiers and officers in a field of battle. This is crucial information in
developing topologies and cases to best represent the MANETs. Another important theory that was
covered was the development of network topologies. The different kinds of network topologies
were revealed and explained. The best-fit topologies were then chosen as bases for the
development of the MANET topologies. Finally, the learning’s of military structure, network
topologies as well as information gathered from meetings with the DST Group were utilized in the
development of network topologies and cases/scenarios that can be inputted to a simulation
system.
This leads directly onto the next chapter, Chapter 5 – Simulations. The developed topologies and
scenarios are now inputted into network simulation software to run and evaluate the result of
running the OSPF routing protocol upon said network topologies and scenarios.
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Chapter 5 – Simulations
The following chapter will cover the network topologies and cases/scenarios that were developed in
the previous Chapter 4 - Simulation Design as they are run and evaluated via the network simulation
software OPNET Network Simulator. This chapter covers the last portion of the Strategy/Result as
well as the Evaluation phase of the methodology covered in Chapter 3 – Methodology. Each of the
cases/scenarios has been separated into Simulation Phases. Each phase represents a grouping of
network topologies/cases/scenarios that are suited towards the same comparative study. The
following chapter is structured into splitting each of these Phases, and then each of the cases
internal to that phase. Each case will then be explained, prediction of the results of OSPF’s behaviour
on the network, the results themselves in graphical and tabulated form, and finally an explanation of
the results given.
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5.1 Simulation Phases
The following section will go into detail of the separate phases of the simulations that were
undertaken to best represent the military MANETs associated with the military structure that will be
utilized out in the battlefield. As explained in the Chapter 5 introduction, phases are a compilation of
network topologies/cases/scenarios that are suited towards the same comparative study. This
means that a phase represents the same network topology/design, but with a number of different
cases/scenarios run upon it then compared in the results.
There are some important keywords that may come up in this section that refer to specific features
of the OPNET Network Simulating Tool. They are as follows.
Application Definition – allows us to specify any applications that we wish to simulate traffic over
the network.
Profile Definition – Allows us to specify details on how the applications as defined in Application
Definition will be utilized throughout the simulation.
Failure Recovery – Allows us to specify failures on the network that happen throughout the
simulation. This includes things such as nodes going down, links breaking, etc.
Please note that Phase 1 has been left out of this document as these are ‘test’ cases and do not
impact the results/help in answering the research question. The ‘test’ cases and network
topologies developed in this Phase were solely for use by the DST Group as the initial cases in
assessing the OPNET Network Simulation software. However, the insight gained by this ‘Phase 1’
research was that there is no impact on the results OPNET Network Simulator produced regardless
of link speeds throughout the network. Therefore, the following simulations utilized 10Mbit/sec
link speeds rather than the required 2-5Kbit/sec links, as there is no impact on results.
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5.1.1 Phase 2
The following topology represents the topology of the basic setup of 5 soldiers connected to two
separate platoon networks (see Figure 17). Those Platoon networks are then connected to the above
level Company networks as represented by the top-level routers.
*Note the crosses on the links represent the current failed links. This simulates SO1, SO3 and SO5
being a part of PL1 and SO2, SO4 being a part of PL2.
Each of the IP addresses used in the simulation setup is also provided below in Table 5.
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IF1
IF1
IF1
IF6
IF2
IF3
IF4
IF5
IF6
IF1
IF2
IF1
IF2
IF1
IF2
IF1
IF2
IF1
IF2
Figure 17 - Phase 2 Overall Topology
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IF1
IF2
IF3
IF4
IF5
Table 5 - Phase 2 IP Table
Device
CO1
Area
3
Interface
IP Address
Subnet Mask
IF1
192.168.6.1
/30
LB0
192.168.7.1
/30
CO2
3
IF1
192.168.5.1
/30
LB0
192.168.8.1
/30
PL1
1
IF1
192.168.6.2
/30
IF2
192.168.1.2
/30
IF3
192.168.1.6
/30
IF4
192.168.1.10
/30
IF5
192.168.1.14
/30
IF6
192.168.1.18
/30
PL2
2
IF1
192.168.2.2
/30
IF2
192.168.2.6
/30
IF3
192.168.2.10
/30
IF4
192.168.2.14
/30
IF5
192.168.2.18
/30
IF6
192.168.5.2
/30
SO1
1
IF1
192.168.1.1
/30
IF2
192.168.2.1
/30
SO2
2
IF1
192.168.1.5
/30
IF2
192.168.2.5
/30
SO3
1
IF1
192.168.1.9
/30
IF2
192.168.2.9
/30
SO4
2
IF1
192.168.1.13
/30
IF2
192.168.2.13
/30
SO5
1
IF1
192.168.1.17
/30
IF2
192.168.2.17
/30
As seen in the above Table 5, each of the physical sides of the network are separated into Areas;
respectfully, Area 1, Area 2 and Area 3.
The basis of the simulation was to setup each of the soldiers to advertise their network as an OSPF
route to their respective PL gateway.
Note: Both CO routers have a Loopback interface setup for simulation of traffic out to the COs and
beyond from the SO level.
Each of the simulations was performed over a 600 second (10min) span.
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The above Figure shows the base OSPF Timer configurations. It is also important to note that 10Mbit
links were utilized throughout the simulation. These configurations were left as default, as they are
the default OSPF configurations in the real world. This ensures an accurate representation of real
world OSPF performance.
5.1.1.1 Case 1 – No Summary Route, No Routing Exposure within PL MANET
The initial case was developed with the intention of getting a base line figure for OSPF routing
overhead on this particular network topology. This means that there will be no elements that give
OSPF a lower bandwidth consumption (i.e. creating the maximum amount of routing overhead for
this case). For this reason the decision to run the simulation with no summary route and no routing
exposure was made. For the definition of Summary Route and Routing Exposure please refer to
Chapter 2, Section 2.4.4.2.
Upon running this simulation, the confirmation of the correct adding of routes needs to be checked
via means of the outputted IP forwarding table for both CO and PL networks. To confirm whether or
not the routing has been setup correctly, we will confirm in each CO and PL routing table that only
the 192.168.1.x SOs and 2.x SOs for each area (1 or 2) should be visible in these tables. This is a
prediction that comes with the end result of the IP forwarding table to ensure the correct addition of
routes.
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5.1.1.2 Case 2A – No Summary Route, Routing Exposure within PL MANET
For this case we will be again using the exact same topology as before, but this time we will be
simulating exposure by moving SOs between PL networks. Namely for this simulation, we initially
have all soldiers connected to PL1, and will be moving SO3 and SO5 from PL1 to PL2 by means of
disconnecting and connecting links between those respective SOs and the designated PL networks.
We will be performing this via the Failure Recovery object of OPNET.
We will be initially disabling all links between all SOs to PL2.
At 300 sec (1/2 time simulation) we will disable links PL1->SO3 and PL1->SO5, then at 400 seconds
(to give time for movement) we will recover the links PL2->SO3 and PL2->SO5. This simulates the
movement of SO3 and SO5 from PL1 to PL2, given 100 seconds of down time for both nodes.
The topology diagram is given below for initial setup. Again all of the links and nodes have OSPF
setup on them, using standard 10Mbit Ethernet links as before.
Figure 18 - Case 2A Topology
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5.1.1.3 Case 2B – Address Summarization, No Routing Exposure in PL MANET
For this case we are still using the same topology as both previous cases. This relates more to Case 1
except with Summary Routes set up on both PL1 and PL2. Note both CO1, CO2 and the lower level PL
networks are on separate networks to allow Area Summarization to occur. Initially you will see that
SO1, SO3, and SO5 are connected to PL1 network, and SO2 and SO4 are connected to PL2 network.
This simulation is setup to determine the difference in OSPF traffic load when using area
summarization versus performance as in previous cases with no summarization and all routes being
advertised.
Figure 19 - Case 2B Topology
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5.1.1.4 Case 2C – Address Summarization, Routing Exposure within PL MANET
For this scenario we are simulating an extension on the case 2A and 2B where we are using Address
Summarization and Routing Exposure within the MANET to show Traffic Loss when SOs switch
between PL networks.
As before, the routing topology remains the same and can be seen as follows with the included
traffic flows:
Figure 20 - Case 2C Topology
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Please refer to Case 2A for OSPF Traffic Sent/Received/Point to Point Throughput as the Results are
identical.
5.1.2 Phase 3
The following section will outline the final large-scale topology of the MANET field simulation. The
following simulation is done at the BN level which includes the vicinity of ~700 SOs on the network.
This is the first simulation performed that utilizes sub networking features of OPNET Simulator. As
previous simulations, all other configurations have been adhered to with the time limit remaining at
10minutes for the simulation. OSPF Efficiency has been disabled as previously, as well as RIP
Efficiency for this example.
The simulation does not factor into account the configuration within each of the networks as
previously described in Section 4.3. In this simulation each of the SOs within the PL networks have
been simulated via Loopback interfaces in a 10.x.y.z IP configuration for simple traceability. This will
be outlined further in the topology diagrams and explanations as follows.
Figure 21 - Top Level Topology
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The above diagram (Figure 21) shows the top level topology. As can be seen there are two links from
the BN to each of the CO networks for redundancy purposes as outlined in the proposal. Each of
these links are currently operating at 10Mbps, but can be easily scaled for simulating the
bottlenecking of the OSPF and RIP routing protocol analysis.
It is also important to note at this stage all of the links utilized are OSPF between the BN network
and the corresponding CO networks. Each of the COs operate in their own Areas that correspond to
the number identifier of the CO networks. I.e.) CO1 is in Area 1, CO2 is in Area 2, etc. BN network is
in Area 0. Each CO includes 3 PL networks, each with 30 soldiers.
Figure 22 - BN Sub Network Topology
The above diagram (Figure 22) represents the internal BN network topology. This shows the BN_HUB
and the routers that connect the BN network via twin links to each of the CO networks. Again, at this
level, each of the links are OSPF. It is also important to note that the Area change over occurs
between the ABR routers internal to the BN network to each of the COs. In this case, toCOx_y will
handle the intra-area linking.
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Figure 23 - CO Sub Network Topology
The above Figure 23 represents the internal CO network topology. As can be seen, similarly to the
BN sub network there is a HUB router that handles all of the routing between the three internal PLs
and the BN network. There are still two links configured between routers and the PL networks for
redundancy purposes. It is also important at this stage to note that ALL links below the toPLx_SOy
are OSPF and all that are above are handled with RIP Routing as specified in the proposal.
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Figure 24 - PL Sub Network Topology
OSPF Base Parameters
Figure 25 - OSPF Configuration, Phase 3
The above Figure 25 shows the base OSPF Timer configurations.
**It is also important to note that 10Mbit links were utilized throughout the simulation.
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Finally, the above diagram (Figure 24) represents the internal PL network topology. Please ignore the
messy links off of the SOs; this is just a bug in OPNET Simulator when dealing with single nodes
inside a sub network. Each of the SOs includes 15 loopback interfaces on them to simulate 30
soldiers within each of the PL networks. The IP configuration of these loopback interfaces has been
configured as follows for easy traceability:
10.x.y.z
x = CO network
y = PL network
z = SO number
It is also important at this stage to note that all of the interfaces between routers of sub networks
have been left to auto assignment via OPNET. Therefore the IP configurations have been assigned by
OPNET for simplicity of design as well as the design not needing specific IP configuration between all
of the interfaces.
5.1.2.1 Case 1 – No Link Fails, Full Connectivity
The following case represents a full connectivity scenario with no link failures. This will not show any
redundancy working as none of the links will fail between the respective PLs, COs and/or BN. For the
following case we will trace the IP Forwarding Tables in BN, CO1 and PL1 up the network tree. As this
case will have no link failures, we can assume that the tables will correspond for each of the other
COs and PLs.
5.1.2.2 Case 2 – Link Failures at PL > CO and CO > BN Level
The following case represents the scenario that a link failure should occur at each sub network layer
level. In this case we will be simulating the failure of links between PL1 and CO1, and then CO1 to
BN. This failure simulation is handled on the same graphs as used in the previous case.
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** The link failure between PL1 and CO1 on the toPL1_SO1 > SO1 connection will occur exactly 180
seconds into the simulation.
** The link failure between CO1 and BN on the toBN1 > toCO1_1 will occur exactly 300 seconds into
the simulation.
All configurations have been sustained in regards to IPs and Routing; thus the previous tables in Case
1 can be utilized for this case.
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5.2 Simulation Results
The following section will go through the explanations of the simulation results as described by the
cases in Section 5.1.
5.2.1 Phase 2
This section will go through the results of Phase 2 of the simulation results. Please refer back to the
corresponding description of the cases in Section 5.1 for a reminder of each case and scenario.
5.2.1.1 Case 1 – No Summary Route, No Routing Exposure within PL MANET
To confirm the correct adding of routes, we will check the IP forwarding table for both CO and PL
networks. To confirm whether or not the routing has been setup correctly, we will confirm in each
CO and PL routing table that only the 192.168.1.x SOs and 2.x SOs for each area (1 or 2) should be
visible in the following tables 6, 7, 8 and 9.
Table 6 - PL1 IP Forwarding Table
Table 7 - CO1 IP Forwarding Table
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Table 8 - PL2 IP Forwarding Table
Table 9 - CO2 IP Forwarding Table
Expectations
Next we will investigate the impact of OSPF traffic on the network. We are expecting a bottleneck at
the beginning, then a smooth out gradually over time t after convergence. This bottleneck we are
expecting is an assumption due to the influx of OSPF hello packets that will flood the network after
initial boot up. This flood will provide the initial routing convergence of the network (Network
Discovery – See Chapter 2). Once OSPF has converged, we expect the activity to settle back down.
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OSPF Traffic Sent (bits/sec) for CO1, CO2, PL1, PL2
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OSPF Traffic Received (bits/sec) for CO1, CO2, PL1 and PL2
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Point to Point Throughput between PL1<->CO1 and PL2<->CO2 (bits/sec)
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5.2.1.1 Phase 2 - Case 1 Results Explained
As expected, the first case results show the initial convergence of OSPF in all graphs. The traffic sent
in the first graph (p. 96) shows the peak at ~2500bits/sec by the PL1 router. While this peak is very
high, it does not yet debunk the hypothesis of this research. The peaks are still below the threshold
given in the requirements. That being said, this was a base case for the second Phase with only 5
soldiers on the network. The assumption is made that scaling up higher will do fairly detrimental
things to the network. It is also important to note that in all cases, once convergence happened, the
stable ~200-300 bits/sec activities still leaves plenty of room for applications thus far.
5.2.1.2 Case 2A – No Summary Route, Routing Exposure within PL MANET
Table 10 - IP Forwarding Table of CO1 @ time (200 sec)
Table 11 - IP Forwarding Table of CO1 @ time (600 sec)
For this case we are looking to make sure the desired result of the SOs 3 and 5 ‘move’ from the PL1
network to the PL2 network after the use of the Failure Model.
As seen, each of the correctly configured SOs connected via PL1 have been propagated and
accessible from CO1 router. Therefore, the IP Forwarding table of CO1 has been successfully
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updated once links between SO3 and SO5 were lost via PL1 as shown in comparing Tables 10 and 11.
We can now check the PL1 IP Forwarding Tables at the same time intervals to make sure at the next
level down in the hierarchy (see Tables 12 and 13).
Table 12 - IP Forwarding Table of PL1 @ time (200 sec)
Table 13 - IP Forwarding Table of PL1 @ time (600 sec)
As previously mentioned, the Direct links between the SOs is retained for those that still have
connection; namely SO1, SO2 and SO4. Also note the loopback address of CO1 has correctly been
picked up here as well.
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Table 14 - IP Forwarding table of CO2 @ time (200 sec)
Table 15 - IP Forwarding Table of CO2 @ time (600 sec)
As can be seen in the above tables (Table 14 and Table 15), the OSPF entries for SO3 and SO5 were
correctly added at the CO level approx. 5 and 10 seconds after the initial reconnection to PL2 @
400sec into the simulation. We can now check over PL2s forwarding tables to see the full
convergence of the SOs 3 and 5 across to PL2. We are expecting an initially empty table for PL2 at
the 200 second interval, and then the appearance of the two direct links to SO3 and SO5 at the 600
second interval.
Table 16 - IP Forwarding Table of PL2 @ time (200sec)
Table 17 - IP Forwarding Table of PL2 @ time (600 sec)
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Again, as previously mentioned, the SO3 and SO5 nodes were successfully picked up both at the 400second mark, exactly 100 seconds after disconnection with PL1 300 seconds into the simulation (see
Tables 16 and 17). As can also be seen, the OSPF entry for the loopback @ CO2.
** While not included in full detail for all SO nodes we will show the IP Forwarding Table for SO1 as
below in Table 18:
Table 18 - SO1 IP Forwarding Table
As can be seen, SO1 has the complete access to all required nodes on the network, as one would
describe. In this instance of the simulation there is no link between the CO networks, but a simple
addition of these links will also provide complete connectivity to all SOs on Area 2.
For the purpose of this simulation we have provided the connectivity between nodes in the same
areas; hence the access to only nodes in the 192.168.1.x range and the access to PL and CO networks
on the same Area number.
Expectations
Similarly to the previous case, it is expected that there will be a great amount of initial convergence
activity, particularly on the PL1 and CO1 routers. This is due to the initial connection of all SOs to
only those two routers. It is also expected to see another peak on the graph at the 300 and 400
second mark due to the mobility of SOs 3 and 5 to PL2. This is also a good test of convergence
activity for 5 soldiers to a single point of contact as soon as the network fires up. The convergence
activity was nearly 2500 bits per second initially in the previous case. One would predict this to be
even higher with the addition of two more nodes to the PL1 network upon initial convergence.
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OSPF Traffic Sent (bits/sec) for CO1, CO2, PL1 and PL2
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OSPF Traffic Received (bits/sec) for CO1, CO2, PL1 and PL2
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Point to Point Throughput between PL1<->CO1 and PL2<->CO2 (bits/sec)
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5.2.1.2 Case 2A – Results Explained
As in the expectations, each of the graphs explains the initial predictions. There is a very large initial
peak on PL1. This peak actually exceeds 6400 bits per second. This has already exceeded the given
link speed requirement upon initial convergence. As predicted, the other routers on the network did
not see any large initial convergence figures. PL1 also saw a peak of activity at the 300 second mark
as predicted when the two SOs left the network. There is a slight break of activity after the
convergence of the SOs leaving. Once the soldiers reconnected at the 400-second interval we again
see convergence activity, this time on PL2 as predicted. This peak was unexpectedly high at nearly
2000 bits per second for convergence of only two routes.
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5.2.1.3 Case 2B – Address Summarization, No Routing Exposure in PL MANET
This case relates directly to Case 1, except it has been setup with address summarization to
determine the impact that route summarization has on the overheads of OSPF.
Table 19 - IP Forwarding Table of CO1
Table 20 -IP Forwarding Table of PL1
Table 21 - IP Forwarding Table of CO2
Table 22 - IP Forwarding Table of PL2
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As there is no mobility aspect to this case, the IP Forwarding tables have been shown (Tables 19 to
22) to confirm whether the correct SOs are connected to each of the PLs and whether or not the COs
get these SOs correctly propagated up the chain of command.
Expectations
The expectations of this case are very similar to the Case 1. The key difference being the use of route
summarization. One would expect that the routing convergence activity on the PL networks would
remain almost identical, but there would be fewer loads on the CO convergence.
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OSPF Traffic Sent (bits/sec) for CO1, CO2, PL1 and PL2
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OSPF Traffic Received (bits/sec) for CO1, CO2, PL1 and PL2
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Point to Point Throughput between PL1<->CO1 and PL2<->CO2 (bits/sec)
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5.2.1.3 Case 2B – Results Explained
As in the expectations, the results shown in the Case 2B graphs are nearly identical to that in Case 1.
There is an ever so slight reduction in the OSPF traffic sent in the initial convergence, but this
difference is within 100bits per second, making the difference almost negligible whether or not
route summarization is used.
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5.2.1.4 Case 2C – Address Summarization, Routing Exposure within PL MANET
Expectations
For this case, we expect the simulation lose traffic that is being sent from CO1 to SO3 and SO5 as
there will be no connection to these soldiers once they have switched to the other PL network. The
convergence figures we expect to remain the same, as previously proved there is no real difference
between having address summarisation on. As the simulation is an extension of Case 2A and 2B, the
results of convergence figures are expected to be the same as Case 2A.
Results
Please refer to Case 2A for OSPF Traffic Sent/Received/Point to Point Throughput as the Results are
identical. The IP Ping Requests and Receives from CO1 to SO3/SO5 can be seen on the following
page.
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IP Ping Requests and Receives from CO1 to SO3/SO5 (Failed Nodes @ t=300sec)
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5.2.1.4 Case 2C – Results Explained
As can be observed, the ping requests failed at t=300 seconds because of the change within the
MANET is not advertised beyond the PL level. It is important to note that the ping requests start at
t=1sec into the simulation and do not get Received until ~62 seconds into the simulation as this is
the time for OSPF Convergence.
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5.2.2 Phase 3
5.2.2.1 Case 1 – No Link Fails, Full Connectivity
The following IP Forwarding Tables have been included in this document as a reference back to the
automatic configuration of IP Addresses in the full-scale scenario. This helps with the debugging
process if one of the nodes is not connected properly to the network. It is also important to note
that, as this is a full-scale implementation, the IP Forwarding tables may not be their full size as there
are in excess of ~700 nodes on this network.
Table 23 - CO1 > PL1 > SO1 IP Forwarding Table
Table 24 - CO1 > PL1 > SO2 IP Forwarding Table
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Table 25 - CO1 > CO1_HUB IP Forwarding Table
It is important to note in IP Forwarding Table 25, the results of OPNET and its OSPF configuration
advertising the entire interface IPs of every other router on the network. The IP Forwarding table is
longer than the above snapshot, but it is just full of the IP addresses of the interfaces of redundancy
connections between routers elsewhere in the network.
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Table 26 - BN > BN_HUB IP Forwarding Table
Again, similarly to the previous scenario with the CO1_HUB table (Table 25), we find that on the
BN_HUB router, all of the 10.x.y.z addresses are there as we required, but so are the interfaces
elsewhere on the network that have been advertised via the OSPF protocol throughout the network
(see Table 26).
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Expectations
The expected results would have a dramatic OSPF convergence figure after the results of Phase 2.
With the full scale (all nodes) on this network (confirmed in IP Forwarding Tables), the expected
results are well in excess of the transmission rates on offer by the equipment. We also predict the
resting network traffic almost being too high for other applications to run upon the network.
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RIP Traffic Sent (bits/sec) for CO1 > PL1 > SO1 (same for all other SOs)
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RIP Traffic Received (bits/sec) for CO1 > PL1 > SO1 (same for all other SOs)
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OSPF Traffic Sent (bits/sec) for CO1_HUB, CO2_HUB, CO3_HUB
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OSPF Traffic Received (bits/sec) for CO1_HUB, CO2_HUB, CO3_HUB
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OSPF Traffic Sent (bits/sec) for BN_HUB
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OSPF Traffic Received (bits/sec) for BN_HUB
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5.2.2.1 Case 1 – Results Explained
As predicted, the results of the OSPF Traffic across all main hub devices are higher than the
capability of the devices they will run on. This confirms in the case of full connectivity, a network of
this scale has a convergence that would bottleneck even a direct Ethernet connection. RIP routing
results have also been added for completeness, but are not the focus of this research. As a side
node, it is interesting to note that the RIP routing network consumption was relatively low, peaking
at only ~59 bits per second. On the other hand, the lowest OSPF traffic was still in excess of 28,000
bits per second, making it unfeasible on even higher capacity networks.
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5.2.2.2 Case 2 – Link Failures at PL > CO and CO > BN Level
Again, the following IP Forwarding Tables have been included in this document as a reference back
to the automatic configuration of IP Addresses in the full-scale scenario. This helps with the
debugging process if one of the nodes is not connected properly to the network. It is also important
to note that, as this is a full-scale implementation, the IP Forwarding tables may not be their full size
as there are in excess of ~700 nodes on this network.
Table 27 - PL1 > SO1 IP Forwarding Table
Table 28 - CO1 > PL1 > SO2 IP Forwarding Table
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Table 29 - CO1 > CO1_HUB IP Forwarding Table
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Table 30 - BN > BN_HUB IP Forwarding Table
Expectations
The results that are expected are similar to the previous case, but with the element of link failure
similar to in Phase 2. As previously shown, the convergence activity of just 2 nodes almost exceeded
the capacity of the network, thus the convergence when ~30 nodes initially leave the network (when
PL1s link fails from CO1 180 seconds into the simulation), then again when CO1s link fails at 300
seconds into the simulation.
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RIP Traffic Sent (bits/sec) for CO1 > PL1 > SO1
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RIP Traffic Recieved (bits/sec) for CO1 > PL1 > SO1
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OSPF Traffic Sent (bits/sec) for CO1_HUB, CO2_HUB, CO3_HUB (ZOOMED)
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OSPF Traffic Received (bits/sec) for CO1_HUB, CO2_HUB, CO3_HUB (ZOOMED)
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OSPF Traffic Sent (bits/sec) for BN_HUB
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OSPF Traffic Received (bits/sec) for BN_HUB
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5.2.2.2 Case 2 – Results Explained
As predicted in the Expectations, the convergence was the same at the beginning of the simulation
(not shown due to zoomed in results to show convergence upon link failure). As shown in the
graphs, the link failure sparked OSPF activity nearly in excess (PL1 disconnect) as well as in excess
(CO1 disconnect) of the available bandwidth according to the requirements. It is also interesting to
note the RIP traffic received by SO1 on CO1 drop off after the disconnection of PL1 as one would
expect.
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5.3 Summary of Simulation Results
The results of the simulations have provided both reasonable and surprising results based upon past
results and predictions of the OSPF protocol in certain situations. The OSPF routing protocol has
much greater routing overheads than expected when placed in such a networking environment.
Being a proactive routing protocol, it was not expected that OSPF would perform well in the MANET
configuration. Routing overheads were much greater than anticipated upon initial convergence.
Once the mobility model was introduced, the convergence numbers were again very high.
There were many interesting points of discussion regarding each set of results when comparing
them against the initial Routing Overheads in Chapter 2, Section 2.4.4.1 – Routing Overheads. One of
the most prevalent proven factors of the Routing Overheads was the increase in number of nodes
having a dramatic effect on both routing overhead during convergence and the network activity
once convergence had occurred. In all cases, this was apparent, with an increase in number of nodes
on the network having a proportional increase in the routing overhead of OSPF.
Another interesting point that was proven came in the form of link speeds and the movement model
having an impact on routing overheads. As discovered with the results, OPNET Simulator did not
show the effect that reduced link speeds have in the simulation results. There was no impact in the
results no matter what the link speeds were. This can be pinpointed to a design with the OPNET
simulation software itself. The software was not designed to show the impact that link speeds have
upon routing overheads, and will thus display the impact that OSPF/protocols/applications have
themselves, rather than the effect it will have once the link bandwidth is exceeded. This can
therefore be a point of further research and simulation. As stated before, the effect that the mobility
model has on routing overheads is apparent, with the routing overhead increasing and becoming
more prevalent (especially with convergence) in the cases that included a mobility model.
Lastly, one of the most interesting factors that were actually proven to have no impact included the
use of summary routes. This element of routing overhead influence did not have a detrimental effect
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on the simulation results when it was used. It could therefore be concluded from this set of results
that it has a negligible effect on OSPF routing overheads within a MANET.
Finally, it is important to note that the increase in network complexity is obviously going to have an
impact on the routing overheads of a protocol. This is a useful measurement of performance of the
protocol in a situation such as a MANET. With the results that have been gathered for the use of
OSPF on a military MANET, the support for other applications will be nearly impossible once the
overheads and usability of the routing protocol has been compensated on the network. It is
therefore conclusive that OSPF in its current form is not suitable for use on a military MANET as per
requested.
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Chapter 6 – Conclusions and Future Work
Starting from the literature review, MANETS appear to be completely different from a typical
structured network. MANETs require a lot more special attention prior to their setting up, as proven
in the literature review. It is important to note that while MANETs do not normally perform as well
as structured networks, their features and flexibility are desirable in certain fields due to their selfconfiguring nature, and low maintenance when compared to a structured network architecture. That
being said, MANETs require a lot of thought and attention when deciding what routing protocol
should be utilized upon the network. ‘Off the shelf’ routing algorithms such as OSPF and RIP pose as
a viable candidates to use on a MANET mainly due to their widespread and knowledge around the
globe. That being said, as proven in the literature review, theoretically they do not perform well on
MANETs. This sparked the interest of the DST Group whom were looking at getting a comprehensive
review of OSPF upon a military style MANET, as the topic had never been covered prior.
One of the most challenging and interesting points when looking at the usage of a MANETs in
comparison to a structured network is the utilization of end devices as the router. Routing
overheads are therefore one of the main issues that will plague the entire network, as each end
devices is essentially a ‘router’ of sorts. Since these end devices do not normally have the
internals/structure or performance of a router, it is important to reduce these routing overheads to
a minimum, to allow maximum network resources and processing power of the end devices to the
applications that are required on said networks. One of the major routing overheads/concerns, as
shown in the simulations was the size of the overall network, in which the size and complexity of the
network had the greatest effect on routing overheads, and thus, performance of the network.
Each of the influences covered in the literature review had a direct impact on the routing overheads
of OSPF except for Link Speeds and Summary Routes. As discussed in the simulation results, this was
due to Link Speeds not being a feature that impacted results of OPNET simulator, becoming a
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software constraint. The other influence of Summary Routes was proven to have a negligible effect
on simulation results.
It can therefore be concluded, through the results gathered and analysed, that OSPF in its current
‘off the shelf’ form is not a viable solution for use on a military MANET. There are many aspects of
the OSPF routing algorithm that concern the network performance due to high routing costs and
overheads. The major of which is convergence, both upon initial setup of the network, but also in
regards to the mobility model which is a detrimental requirement of a MANET. If full summarization
is performed, full IP connectivity is ‘plausible’, but again, this comes with the loss of the mobility
model, which is a detrimental requirement of MANETs. It is also revealed that the use of OSPF is
viable in a network of a very low number of nodes without a mobility mode. This is however a
detrimental requirement of a MANET. It can therefore be concluded that the off the shelf OSPF
routing algorithm is not a viable routing protocol for use in military MANETs.
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6.1 Future Work
The state of this thesis is complete in regards to the thorough research and analysis of the affects of
OSPF on a military style MANET. That being said, there are still elements to this thesis that can be
further expanded upon. The main of which is the inclusion of other off the shelf routing algorithms
such as RIP. This expansion to other off the shelf routing algorithms will allow further studies into
finding a better fit, and possibly a protocol that performs well in its ‘off the shelf’ form. This can then
be analysed and compared with the results of this and other research to determine other features
and algorithms that best suit MANETS.
Another lead for further works from this research is the inclusion of the communication and radio
manufacturers that design and develop the devices that will be used out in the field of work where
the MANETs are required. Working with these manufacturers will allow the simulations models to be
further fine tuned to more accurately represent the real world scenarios and devices. The behaviour
of said devices can be better interpreted and inputted to the simulation software to enhance the
accuracy of results of OSPF running upon said end devices. Working with the device manufacturers
will also give an insight into the inner working and technology platform within said end devices. This
will allow another point of expansion for this research in finding a routing algorithm that best suits
the devices. By working closely with the manufacturers of radio devices, the routing algorithms that
best suit the workings and platforms of the devices can be discovered and fine-tuned to suit.
Lastly, one of the key future works for this paper in particular, with the focus still on OSPF’s use in
military MANETs, is the research of off the shelf OSPF adapted MANET routing protocols. As touched
upon in the literature, OSPF-MDR is a MANET focused extension of OSPF. While the algorithm is still
in experimental stages, the internal workings of the protocol can be adapted for use in simulation
tools such as OPNET. This will act as a terrific comparison platform to the research that was
undertaken in this paper. It will allow a direct comparison to the traditional OSPF protocol used in
this document, but will also allow further fine-tuning and development of the OSPF-MDR algorithm.
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6.2 Thesis Contribution
1. OSPF in a military MANET situation is unlikely to be viable with the mobility model.
The viability for the use of the OSPF routing protocol in a military MANET situation has been
proven to be an infeasible task given the set of specifications as per required. As revealed in
Chapter 5, Section 5.2.1.2, it was proven that with the mobility model in place, the routing
overheads of OSPF were far greater than expected upon the convergence of the re-entry of
nodes into the network. With the requirements of a 2-5Kbit per second link, the routing
overhead sits at nearly 2Kbit upon convergence, consuming most, if not all, of the available
network resources.
2. With a low number of nodes (less than 5 soldiers), the use of RIP and/or OSPF might be a
viable routing solution on a military MANET.
As initially explained in Section 2.4.4.2, the number of nodes upon the network was revealed
through literature to be a key factor in influencing routing overhead. This was proven in
Section 5.2.1.1, where by the routing overhead of OSPF after the initial convergence was
within acceptable range as per given in the requirements. The stable routing overhead sit
well below the 2-5Kbit per second maximum network bandwidth, with room left for other
applications upon the network.
3. OPNET Network Simulation model for military MANETs.
Military style MANETs have been modelled and simulated through the use of the OPNET
Network Simulator as shown in Chapter 4 – Simulation Design. It is important to note the
development of the two main styles of network topologies to simulate different detail levels
of a military MANET. Section 4.3.3.2 best reveals these two main styles regarding a full scale
implementation (expected ~700 nodes on the MANET in total), as well as the lower level,
more detailed topology of 5 nodes.
4. Expansion of the understanding of use of MANETS within the hierarchical structure of the
Military and the use of the MANETS within this structure.
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It has been revealed in Chapter 4 the development of network topologies and cases to best
represent the structure and usage of military MANETs. This development required the
expanded understanding of the use of MANETs within the military environment and
structure. This understanding is revealed in Sections 4.1 for Military Structure, 4.2 for
Network Topologies and combined in Section 4.3 whereby the development of network
topologies and scenarios is undertaken.
5. Expand the understanding of the limitations of the OSPF routing algorithm.
It has been revealed in the Chapter 6 the conclusive evidence that OSPF has a multitude of
limitations impacting its use on military MANETs. It has been revealed that the major
impacts regarding routing overheads for OSPF on a military network include number of
nodes on the network, movement/routing exposure as well as traffic loads. This provided
insight into the limitations whereby OSPF ‘falls down’ in regards to its use on a military
MANET.
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[38]RFC5614 |
| Ogier, R. and P. Spagnolo, "Mobile Ad Hoc Network (MANET) Extension of
OSPF Using Connected Dominating Set (CDS) Flooding", RFC 5614, DOI 10.17487/RFC5614,
August 2009, <http://www.rfc-editor.org/info/rfc5614>.
[39]RFC5820 |
| Roy, A., Ed., and M. Chandra, Ed., "Extensions to OSPF to Support Mobile
Ad Hoc Networking", RFC 5820, DOI 10.17487/RFC5820, March 2010, <http://www.rfceditor.org/info/rfc5820>.
[40]Du, Ning, Huijing Yang, and Chunying Wang. "An Optimized OSPF Routing Protocol for
Mobile Ad-hoc Networks." Journal of Networks 7.9 (2012): 1456-1463.
[41]James, Shakir. "OSPF Extensions for Mobile Ad-hoc Networks." Washington University in St.
Louis (2008).
[42]Pan, Jianli, and Raj Jain. "A survey of network simulation tools: Current status and future
developments." Email: jp10@ cse. wustl. edu (2008).
[43]Siraj, S., A. Gupta, and R. Badgujar. "Network simulation tools survey." International Journal
of Advanced Research in Computer and Communication Engineering 1.4 (2012): 199-206.
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at: http://apus.uma.pt/vns/ [Accessed 27 Nov. 2015].
[45]Sarkar, Nurul I., and Syafnidar A. Halim. "A review of simulation of telecommunication
networks: simulators, classification, comparison, methodologies, and recommendations."
(2011).
[46]Crnkovic, I., “Software Engineering and Science,” vol. 2003: Malardalen University, 2001.
[47]Orebaugh, Angela, Gilbert Ramirez, and Jay Beale. Wireshark & Ethereal network protocol
analyzer toolkit. Syngress, 2006.
[48]Department of Defense (1999). Department of defense, interface standard, common
warfighting symbology: MIL-STD-2525B. Washington DC: Department of Defense, Defense
Information Systems Agency. Available at http://symbology.disa.mil/symbol/index.html.
[49]Axis & Allies Wiki, (2015). Military Symbols. [online] Available at:
http://axisandallies.wikia.com/wiki/Military_Symbols [Accessed 29 Nov. 2015].
[50]Olive-drab.com, (2015). U.S. Army Organization. [online] Available at: http://olivedrab.com/od_milorgs_us_army.php [Accessed 29 Nov. 2015].
[51]Sudarshansoftech.com, (n.d.). Computer H/W & Networking. [online] Available at:
http://www.sudarshansoftech.com/chnt3.htm [Accessed 30 Nov. 2015].
[52]Baccelli, Emmanuel, Juan Antonio Cordero Fuertes, and Philippe Jacquet. "Ospf over multihop ad hoc wireless communications." International journal of Computer Networks &
Communications 2.5 (2010): 37-56.
[53]Cisco, (2005). OSPF Design Guide. [online] Available at:
http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/70391.html#t8 [Accessed 29 Nov. 2015].
Page 149
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